Updated on 2024/05/14

写真a

 
Kentaro Kuga
 
Organization
Graduate School of Engineering Department of Advanced Science and Technology Materials Science and Engineering Energy Materials Laboratory Commissioned Researcher   
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Research Areas

  • Natural Science / Magnetism, superconductivity and strongly correlated systems

Main research papers

Education

  • The University of Tokyo

    - 2011.3

Papers

  • Huge Peltier conductivity in valence fluctuating material Yb3Si5 Reviewed

    Kentaro Kuga, Keisuke Hirata, Masaharu Matsunami, Tsunehiro Takeuchi

    Applied Physics Letters   123 ( 20 )   2023.11 （   ISSN:0003-6951 ）

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1063/5.0172472

  • Observation of a critical charge mode in a strange metal Reviewed

    Hisao Kobayashi, Yui Sakaguchi, Hayato Kitagawa, Momoko Oura, Shugo Ikeda, Kentaro Kuga, Shintaro Suzuki, Satoru Nakatsuji, Ryo Masuda, Yasuhiro Kobayashi, Makoto Seto, Yoshitaka Yoda, Kenji Tamasaku, Yashar Komijani, Premala Chandra, Piers Coleman

    Science   379 ( 6635 )   908 - 911   2023.3 （   ISSN:0036-8075   eISSN:1095-9203 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

    Understanding the strange metallic behavior that develops at the brink of localization in quantum materials requires probing the underlying electronic charge dynamics. Using synchrotron radiation-based Mossbauer spectroscopy, we studied the charge fluctuations of the strange metal phase of beta-YbAlB4 as a function of temperature and pressure. We found that the usual single absorption peak in the Fermi-liquid regime splits into two peaks upon entering the critical regime. We interpret this spectrum as a single nuclear transition, modulated by nearby electronic valence fluctuations whose long time scales are further enhanced by the formation of charged polarons. These critical charge fluctuations may prove to be a distinct signature of strange metals.

    DOI： 10.1126/science.abc4787

  • Anisotropy-driven quantum criticality in an intermediate valence system. Reviewed

    Mihael S Grbić, Eoin C T O'Farrell, Yosuke Matsumoto, Kentaro Kuga, Manuel Brando, Robert Küchler, Andriy H Nevidomskyy, Makoto Yoshida, Toshiro Sakakibara, Yohei Kono, Yasuyuki Shimura, Michael L Sutherland, Masashi Takigawa, Satoru Nakatsuji

    Nature communications   13 ( 1 )   2141 - 2141   2022.4 （     eISSN:2041-1723 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PORTFOLIO  

    Intermetallic compounds containing f-electron elements have been prototypical materials for investigating strong electron correlations and quantum criticality (QC). Their heavy fermion ground state evoked by the magnetic f-electrons is susceptible to the onset of quantum phases, such as magnetism or superconductivity, due to the enhanced effective mass (m*) and a corresponding decrease of the Fermi temperature. However, the presence of f-electron valence fluctuations to a non-magnetic state is regarded an anathema to QC, as it usually generates a paramagnetic Fermi-liquid state with quasiparticles of moderate m*. Such systems are typically isotropic, with a characteristic energy scale T0 of the order of hundreds of kelvins that require large magnetic fields or pressures to promote a valence or magnetic instability. Here we show the discovery of a quantum critical behaviour and a Lifshitz transition under low magnetic field in an intermediate valence compound α-YbAlB4. The QC origin is attributed to the anisotropic hybridization between the conduction and localized f-electrons. These findings suggest a new route to bypass the large valence energy scale in developing the QC.

    DOI： 10.1038/s41467-022-29757-9

  • Simultaneous enhancements of thermopower and electrical conductivity in quasi-one-dimensional α-YbAlB4 single crystal Reviewed

    Kentaro Kuga, Masaharu Matsunami, Saurabh Singh, Satoru Nakatsuji, Tsunehiro Takeuchi

    Applied Physics Letters   119 ( 22 )   2021.11 （   ISSN:0003-6951   eISSN:1077-3118 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

    We report the thermoelectric properties of valence fluctuating material alpha-YbAlB4 along a-, b-, and c-axes. The temperature dependence of the Seebeck coefficient for all axes shows negative peaks at around 250 K, which is close to the Kondo scale. Interestingly, the absolute value of the Seebeck coefficient along c-axis (-75 mu V K-1 at 250 K) is larger than those along a- and b-axes (-50 mu V K-1 at 250 K) although the electrical resistivity along c-axis is about four times lower than those along a- and b-axes. As a result, a very large thermoelectric power factor of & SIM;14.5 mW m(-1 )K(-2) is realized along c-axis at 200 K, which is ten times larger than those along a- and b-axes. The anisotropies in electrical resistivity and Seebeck coefficient, respectively, have different origins of Fermi surface and the c-f hybridization, realizing the simultaneous enhancements of thermopower and electrical conductivity.

    DOI： 10.1063/5.0073038

  • Strange metal without magnetic criticality Reviewed

    Takahiro Tomita, Kentaro Kuga, Yoshiya Uwatoko, Piers Coleman, Satoru Nakatsuji

    Science   349 ( 6247 )   506 - 509   2015.7 （   ISSN:0036-8075   eISSN:1095-9203 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

    A fundamental challenge to our current understanding of metals is the observation of qualitative departures from Fermi liquid behavior.The standard view attributes such non-Fermi liquid phenomena to the scattering of electrons off quantum critical fluctuations of an underlying order parameter. Although the possibility of non-Fermi liquid behavior isolated from the border of magnetism has long been speculated, no experimental confirmation has been made. Here, we report on the observation of a strange metal region away from a magnetic instability in an ultrapure single crystal. In particular, we show that the heavy-fermion superconductor b-YbAlB4 forms a possible phase with strange metallic behavior across an extensive pressure regime, distinctly separated from a high-pressure magnetic quantum phase transition by a Fermi liquid phase.

    DOI： 10.1126/science.1262054

  • Magnetic order induced by Fe substitution of Al site in the heavy-fermion systems α-YbAlB<inf>4</inf> and β-YbAlB<inf>4</inf> Reviewed

    Kentaro Kuga, Gregory Morrison, Larico Treadwell, Julia Y. Chan, Satoru Nakatsuji

    Physical Review B - Condensed Matter and Materials Physics   86 ( 22 )   224413-1 - 6   2012.12 （   ISSN:1098-0121   eISSN:1550-235X ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

    β-YbAlB4 is a heavy-fermion superconductor that exhibits a quantum criticality without tuning at zero field and under ambient pressure. We have succeeded in substituting Fe for Al in β-YbAlB4 as well as the polymorphous compound α-YbAlB4, which in contrast has a heavy Fermi-liquid ground state. Full structure determination by single-crystal x-ray diffraction confirmed no change in crystal structure for both α- and β-YbAlB4, in addition to volume contraction with Fe substitution. Our measurements of the magnetization and specific heat indicate that both α-YbAl0.93Fe0.07B4 and β-YbAl0.94Fe0.06B4 exhibit a magnetic order, most likely of a canted antiferromagnetic type, at 7∼9 K. The increase in the entropy as well as the decrease in the antiferromagnetic Weiss temperature with the Fe substitution in both systems indicates that the chemical pressure due to the Fe substitution suppresses the Kondo temperature and induces the magnetism. © 2012 American Physical Society.

    DOI： 10.1103/PhysRevB.86.224413

  • Spin-orbital short-range order on a honeycomb-based lattice Reviewed

    S. Nakatsuji, K. Kuga, K. Kimura, R. Satake, N. Katayama, E. Nishibori, H. Sawa, R. Ishii, M. Hagiwara, F. Bridges, T. U. Ito, W. Higemoto, Y. Karaki, M. Halim, A. A. Nugroho, J. A. Rodriguez-Rivera, M. A. Green, C. Broholm

    Science   336 ( 6081 )   559 - 563   2012.5 （   ISSN:0036-8075   eISSN:1095-9203 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

    Frustrated magnetic materials, in which local conditions for energy minimization are incompatible because of the lattice structure, can remain disordered to the lowest temperatures. Such is the case for Ba 3CuSb2O9, which is magnetically anisotropic at the atomic scale but curiously isotropic on mesoscopic length and time scales. We find that the frustration of Wannier's Ising model on the triangular lattice is imprinted in a nanostructured honeycomb lattice of Cu2+ ions that resists a coherent static Jahn-Teller distortion. The resulting two-dimensional random-bond spin-1/2 system on the honeycomb lattice has a broad spectrum of spin-dimer-like excitations and low-energy spin degrees of freedom that retain overall hexagonal symmetry.

    DOI： 10.1126/science.1212154

  • Quantum criticality without tuning in the mixed valence compound β-YbAlB<inf>4</inf> Reviewed

    Yosuke Matsumoto, Satoru Nakatsuji, Kentaro Kuga, Yoshitomo Karaki, Naoki Horie, Yasuyuki Shimura, Toshiro Sakakibara, Andriy H. Nevidomskyy, Piers Coleman

    Science   331 ( 6015 )   316 - 319   2011.1 （   ISSN:0036-8075   eISSN:1095-9203 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

    Fermi liquid theory, the standard theory of metals, has been challenged by a number of observations of anomalous metallic behavior found in the vicinity of a quantum phase transition. The breakdown of the Fermi liquid is accomplished by fine-tuning the material to a quantum critical point by using a control parameter such as the magnetic field, pressure, or chemical composition. Our high-precision magnetization measurements of the ultrapure f-electron-based superconductor β-YbAlB4 demonstrate a scaling of its free energy that is indicative of zero-field quantum criticality without tuning in a metal. The breakdown of Fermi liquid behavior takes place in a mixed-valence state, which is in sharp contrast with other known examples of quantum critical f-electron systems that are magnetic Kondo lattice systems with integral valence.

    DOI： 10.1126/science.1197531

  • Superconductivity and quantum criticality in the heavy-fermion system β-YbAlB4 Reviewed

    S. Nakatsuji, K. Kuga, Y. Machida, T. Tayama, T. Sakakibara, Y. Karaki, H. Ishimoto, S. Yonezawa, Y. Maeno, E. Pearson, G. G. Lonzarich, L. Balicas, H. Lee, Z. Fisk

    Nature Physics   4 ( 8 )   603 - 607   2008.8 （   ISSN:1745-2473   eISSN:1745-2481 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

    A long-standing question in the field of superconductivity is whether pairing of electrons can arise in some cases as a result of magnetic interactions instead of electron-phonon-induced interactions as in the conventional Bardeen-Cooper-Schrieffer theory. A major challenge to the idea of magnetically mediated superconductivity has been the dramatically different behaviour of the cerium and ytterbium heavy-fermion compounds. The cerium-based systems are often found to be superconducting, in keeping with a magnetic pairing scenario, but corresponding ytterbium systems, or hole analogues of the cerium systems, are not. Despite searches over two decades there has been no evidence of heavy-fermion superconductivity in an ytterbium system, casting doubt on our understanding of the electron-hole parallelism between the cerium and the ytterbium compounds. Here we present the first empirical evidence that superconductivity is indeed possible in an ytterbium-based heavy-fermion system. In particular, we observe a superconducting transition at Tc=80 mK in high-purity single crystals of YbAlB 4 in the new structural β phase. We also observe a novel type of non-Fermi-liquid state above Tc that arises without chemical doping, in zero applied magnetic field and at ambient pressure, establishing β-YbAlB4 as a unique system showing quantum criticality without external tuning. © 2008 Macmillan Publishers Limited. All rights reserved.

    DOI： 10.1038/nphys1002

  • Orbital hybridisation effects in B2 phase Cr doped Co2MnAl. Reviewed

    Swati Pathak, Saurabh Singh, S Khalid, Kentaro Kuga, Tsunehiro Takeuchi, R Bindu

    Journal of physics. Condensed matter : an Institute of Physics journal   35 ( 39 )   2023.6 （   ISSN:1361-648X ）

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    We investigate here the magnetic, transport, local structural and electronic properties of Co2Mn1-xCrxAl (x= 0, 0.05, 0.1 and 0.2). Our results show that all the compounds stabilise in B2 phase and are ferromagnets. The results reveal disorder at the structural and magnetic levels. X-ray absorption near edge structure (XANES) analysis reveal signature of antisite disorder between Mn and Al atoms with equal ratio. The electronic structure calculations suggest enhancement in the half metallicity, localisation of electrons at the Fermi level and an increment in density of states with doping. The combined results of electronic structure calculations and XANES studies suggest transfer of electrons to the Co site. The results of high temperature resistivity measurements suggest the conduction electrons are undergoing transition from delocalisation to weak localisation to activated behaviour with Cr doping. The extended x-ray absorption spectroscopic analysis shows that the local structure around Mn atom is different from the global structure as obtained from the x-ray diffraction results. The behaviour of the edge region is in line with the trend as obtained from the compositional analysis. We observe link between the hybridisation of 3dlike states at the Mn, Cr sites with that at the Co site and the transport properties. This could help in understanding the unusual decrement in the lattice parameter with doping. These results reveal the role of local structure in understanding the physical properties of such systems.

    DOI： 10.1088/1361-648X/ace092

  • Valence fluctuation in Yb3Si5 probed by synchrotron X-ray photoemission spectroscopy Reviewed

    Kentaro Kuga, Masaharu Matsunami, Hidenori Fujiwara, Goro Nozue, Akane Ose, Akira Sekiyama, Akira Yasui, Satoru Hamamoto, Masaki Oura, Tsunehiro Takeuchi

    Japanese Journal of Applied Physics   62 ( SD )   SD1014 - SD1014   2023.5 （   ISSN:0021-4922   eISSN:1347-4065 ）

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    Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP Publishing  

    Abstract

    We report the direct evidence of valence fluctuation in the thermoelectric material Yb3Si5 by using synchrotron X-ray photoemission spectroscopy. The Yb 3d core level photoemission spectrum of a Yb3Si5 single crystal shows clear separation of the Yb2+ peak and Yb3+ multiplet peaks. From the spectral weight of each component, the mean valence of Yb ions is estimated to be +2.67 at 20 K. Furthermore, a Kondo resonance peak just below the Fermi energy is also observed by high-resolution soft X-ray photoemission spectroscopy, suggesting the valence fluctuating state in Yb3Si5.

    DOI： 10.35848/1347-4065/aca911

    Other Link： https://iopscience.iop.org/article/10.35848/1347-4065/aca911/pdf

  • Thermoelectric performance of Fe2V0.9W0.1Al thin films deposited on n-type Si substrates Reviewed

    Fahmi Machda, Saurabh Singh, Kentaro Kuga, Artoni K. R. Ang, Masaharu Matsunami, Tsunehiro Takeuchi

    Japanese Journal of Applied Physics   62 ( 5 )   2023.5 （   ISSN:1347-4065 ）

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    DOI： 10.35848/1347-4065/accfd7

  • Lattice effects on the physical properties of half-doped perovskite ruthenates Reviewed

    Jaskirat Brar, Saurabh Singh, Kentaro Kuga, Priyamedha Sharma, M. Bharath, Tsunehiro Takeuchi, R. Bindu

    JOURNAL OF PHYSICS-CONDENSED MATTER   35 ( 19 )   2023.5 （   ISSN:0953-8984   eISSN:1361-648X ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing Ltd  

    We investigate the unusual phase transitions in SrRuO3 and Sr0.5Ca0.5Ru 1-x x O-3 (x = 0, 0.05 and 0.1) employing x-ray diffraction, resistivity, magnetic studies and x-ray photoemission spectroscopy. Our results show the compounds undergo a crossover from itinerant ferromagnetism to localized ferromagnetism. The combined studies suggest Ru and Cr be in the 4+ valence state. A Griffith phase and an enhancement in Curie temperature (T ( c )) from 38 K to 107 K are observed with Cr doping. A shift in the chemical potential towards the valence band is observed with Cr doping. In the metallic samples, interestingly, a direct link between the resistivity and orthorhombic strain is observed. We also observe a connection between orthorhombic strain and T ( c ) in all the samples. Detailed studies in this direction will be helpful to choose suitable substrate materials for thin-film/device fabrication and hence manoeuvre its properties. In the non-metallic samples, the resistivity is mainly governed due to disorder, electron-electron correlation effects and a reduction in the number of electrons at the Fermi level. The value of the resistivity for the 5% Cr doped sample suggests semi-metallic behaviour. Understanding its nature in detail using electron spectroscopic techniques could unravel the possibility of its utility in high-mobility transistors at room temperature and its combined property with ferromagnetism will be helpful in making spintronic devices.

    DOI： 10.1088/1361-648X/acc15d

  • Magneto-thermal conductivity effect and enhanced thermoelectric figure of merit in Ag2Te Reviewed

    Keisuke Hirata, Kentaro Kuga, Masaharu Matsunami, Minyue Zhu, Joseph P. Heremans, Tsunehiro Takeuchi

    AIP Advances   13 ( 1 )   2023.1 （   ISSN:2158-3226   eISSN:2158-3226 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

    In this study, we report a large magneto-thermal conductivity effect, potentially usable in heat flow switches and thermoelectric devices, in Ag2Te over a wide temperature range, including room temperature. When a magnetic field of mu H-0 = 9 T is applied to Ag2Te at 300 K along the direction perpendicular to the heat and electric currents, the thermal conductivity kappa decreases by a remarkable 61%. This effect is mainly caused by the suppressed electronic thermal conductivity in association with a significant magnetoresistance effect, but the suppression of the thermal conductivity is larger than that of the electrical conductivity, presumably due to a field-induced decrease in the Lorenz ratio. Its very low lattice thermal conductivity, as low as 0.5 W m(-1) K-1, also greatly contributes to the large relative magneto-thermal conductivity effect. The significant decrease in thermal conductivity and the 18% increase in the Seebeck coefficient S lead to a nearly 100% increase in the thermoelectric figure of merit zT = S-2 sigma T kappa(-1) despite the 43% decrease in electrical conductivity sigma.

    DOI： 10.1063/5.0131326

  • Multicritical phase diagram of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>PrMn</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Sb</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> with two interacting magnetic elements Reviewed

    Takahiro Urata, Yusuke Takahashi, Kentaro Kuga, Tsunehiro Takeuchi, Hiroshi Ikuta

    Physical Review B   106 ( 18 )   2022.11 （   ISSN:2469-9950   eISSN:2469-9969 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

    We carried out systematic magnetotransport measurements to study the magnetic phase diagram of PrMn1-xSb2, where two antiferromagnetic orders associated with the moments of Pr and Mn coexist. When the magnetic field (H) was applied parallel to the crystallographic c axis, we found a tricritical point where a first-to-second order changeover takes place as in ordinary metamagnets. On the other hand, the metamagnetic transition field decreased unexpectedly with decreasing the temperature at low temperatures for H II [110]. Further, the transition line associated with the metamagnetic transition terminated at low temperature, where a multicritical point was formed. Starting from a three-dimensional phase diagram predicted from a simple model and modifying it to fit our experimental results, we argue that the magnetic interaction between the two magnetic elements is responsible for forming the new critical point and influences the shape of the phase boundaries.

    DOI： 10.1103/physrevb.106.184401

    Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.106.184401/fulltext

  • Synthesis and structural link to the electronic and magneto-transport properties of spin-orbit Mott insulator Sr2IrO4. Reviewed

    Priyamedha Sharma, Saurabh Singh, Kentaro Kuga, Tsunehiro Takeuchi, R Bindu

    Journal of physics. Condensed matter : an Institute of Physics journal   34 ( 43 )   2022.8 （   ISSN:0953-8984   eISSN:1361-648X ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing Ltd  

    We investigate the effect of sample preparation conditions on the link between the structural and physical properties of polycrystalline spin-orbit Mott insulator, Sr2IrO4. The samples were prepared in two batches. With the first batch prepared as per the commonly adopted procedure in literature and the second batch prepared adopting the same procedure as the first batch but with an additional annealing in vacuum. Interestingly, our results show that without change in the value of the Curie temperature (TC), there occurs increase in the value of magnetization, resistivity, magneto-resistance (MR) and an increase in temperature range of stabilization of the canted antiferromagnetic structure. The temperature behaviour of the difference in the irreversible magnetization between the samples is in line with the difference in the Ir-O-Ir in-plane bond angle. At low temperatures, the conduction mechanism in the first batch of the sample is mainly governed by disorder while in the case of the other sample it is of Arrhenius type. The magneto-transport results have shown its strong link with the disorder and structural results. Although the nature and mechanism of the disorder needs to be investigated further, the present results throw light on the role of disorder and its connectivity between the structure and physical properties to understand its complex behaviours.

    DOI： 10.1088/1361-648X/ac8961

  • Electronic structure of silver chalcogenides investigated by hard x-ray photoemission spectroscopy and density functional theory calculations Reviewed

    K. Sato, K. Hirata, S. Singh, K. Kuga, F. Ogawa, M. Matsunami, T. Takeuchi

    Journal of Applied Physics   132 ( 4 )   2022.7 （   ISSN:1089-7550 ）

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1063/5.0095987

  • Pressure-induced changes of valence fluctuation in beta-YbAlB4 probed by x-ray Reviewed

    Yui Sakaguchi, Shugo Ikeda, Naomi Kawamura, Masaichiro Mizumaki, Kentaro Kuga, Shintaro Suzuki, Keita Sone, Satoru Nakatsuji, Hisao Kobayashi

    PHYSICAL REVIEW B   105 ( 15 )   2022.4 （   ISSN:2469-9950   eISSN:2469-9969 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

    We report detailed valence fluctuation phenomena in the unique quantum-critical compound 0-YbAlB4 under pressures and at low temperatures. We directly observed the drastic change in the pressure dependence of the mean Yb valence at about 3 GPa with no pressure-induced structural transition. Below 3 GPa, the anomaly in the temperature dependences of the mean Yb valence was observed at about 55 K under ambient pressure, corresponding to a previously observed reduced Kondo coherence temperature, and this temperature rapidly decreases to 22 K at 2.2 GPa, in contrast to the monotonous decrease of the high Kondo temperature (similar to 250 K at ambient pressure). The present results reveal that this reduced Kondo coherence temperature is responsible for the unconventional quantum critical behaviors in beta-YbAlB4. Above 3 GPa, it was found that the temperature dependence of the mean Yb valence exhibits a discontinuous change at low temperature (10.5 and 9 K under 4.8 and 5.5 GPa, respectively).

    DOI： 10.1103/PhysRevB.105.155129

  • Synergetic Enhancement of the Power Factor and Suppression of Lattice Thermal Conductivity via Electronic Structure Modification and Nanostructuring on a Ni- and B-Codoped p-Type Si–Ge Alloy for Thermoelectric Application Reviewed

    Omprakash Muthusamy*, シン　サウラブ, Keisuke Hirata*, Kentaro Kuga, Santhana Krishnan Harish **, Masaru Shimomura **, Masahiro Adachi **, Yoshiyuki Yamamoto **, Masaharu Matsunamii, Tsunehiro Takeuchi

    ACS Applied Electronic Materials   3 ( 12 )   5621 - 5631   2021.12

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    Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

  • Simultaneous enhancements of thermopower and electrical conductivity in quasi-one-dimensional α-YbAlB4 single crystal Reviewed

    Kentaro Kuga, Masaharu Matsunamii, シン　サウラブ, 中辻知 **, Tsunehiro Takeuchi

    Applied Physics Letters   119   223905   2021.12

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  • Simultaneous enhancements of thermopower and electrical conductivity in quasi-one-dimensional α-YbAlB4 single crystal Reviewed

    Kentaro Kuga, Masaharu Matsunamii, シン　サウラブ, Satoru Nakatsuji*, Tsunehiro Takeuchi

    Applied Physics Letters   119 ( 22 )   223905   2021.12

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  • High-temperature antiferromagnetism in Yb based heavy fermion systems proximate to a Kondo insulator Reviewed

    Shintaro Suzuki, Kou Takubo, Kentaro Kuga, Wataru Higemoto, Takashi U. Ito, Takahiro Tomita, Yasuyuki Shimura, Yosuke Matsumoto, Cédric Bareille, Hiroki Wadati, Shik Shin, Satoru Nakatsuji

    Physical Review Research   3 ( 2 )   023140   2021.5 （     eISSN:2643-1564 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

    Given the parallelism between the physical properties of Ce- and Yb-based magnets and heavy fermions due to the electron-hole symmetry, it has been rather odd that the transition temperature of the Yb-based compounds is normally very small, as low as similar to 1 K or even lower, whereas Ce counterparts may often have the transition temperature well exceeding 10 K. Here, we report our experimental discovery of the transition temperature reaching 20 K in a Yb-based compound at ambient pressure. The Mn substitution at the Al site in an intermediate valence state of alpha-YbAlB4 not only induces antiferromagnetic transition at a record high temperature of 20 K but also transforms the heavy-fermion liquid state in alpha-YbAlB4 into a highly resistive metallic state proximate to a Kondo insulator.

    DOI： 10.1103/physrevresearch.3.023140

    Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevResearch.3.023140/fulltext

  • Synergetic Enhancement of the Power Factor and Suppression of Lattice Thermal Conductivity via Electronic Structure Modification and Nanostructuring on a Ni- And B-Codoped p-Type Si-Ge Alloy for Thermoelectric Application Reviewed

    Omprakash Muthusamy, Saurabh Singh, Keisuke Hirata, Kentaro Kuga, Santhana Krishnan Harish, Masaru Shimomura, Masahiro Adachi, Yoshiyuki Yamamoto, Masaharu Matsunami, Tsunehiro Takeuchi

    ACS Applied Electronic Materials   3 ( 12 )   5621 - 5631   2021 （     eISSN:2637-6113 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

    In this study, the strategies of modifying the electronic structure, tuning carrier concentration, and nanostructuring were implemented to improve the power factor and reduce the thermal conductivity of Si-Ge simultaneously. The Si0.65-xGe0.32Ni0.03Bx (x = 0.01, 0.02, 0.03, and 0.04) nanostructure was synthesized by high-energy ball-milling. Subsequently, a high-pressure with low-temperature sintering process was carried out. A small amount of nickel (Ni) and boron (B) was introduced into Si-Ge to modify the electronic structure and optimize the carrier concentration. The sintered sample Si0.62Ge0.32Ni0.03B0.03 showed a high power factor of 2.3 mW m-1 K-2 at 1000 K, which was influenced by the modified electronic structure and optimized carrier concentration. In addition, the thermal conductivity was effectively decreased to 1.47 W m-1 K-1 due to the phonon scattering by the micro to nanoscale grain boundaries. Ultimately, a large dimensionless figure of merit ZT ∼1.56 was obtained at 1000 K. Therefore, following these strategies can improve the thermoelectric performance of earth-abundant, environmentally friendly, and nontoxic Si-Ge material.

    DOI： 10.1021/acsaelm.1c01075

  • Strong in-plane anisotropy in the electronic structure of fixed-valence β- LuAlB4 Reviewed

    Pascal Reiss, Jordan Baglo, Hong'En Tan, Xiaoye Chen, Sven Friedemann, Kentaro Kuga, F. Malte Grosche, Satoru Nakatsuji, Michael Sutherland

    Physical Review B   102 ( 8 )   2020.8 （   ISSN:2469-9950   eISSN:2469-9969 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

    © 2020 American Physical Society. The origin of intrinsic quantum criticality in the heavy-fermion superconductor β-YbAlB4 has been attributed to strong Yb valence fluctuations and its peculiar crystal structure. Here, we assess these contributions individually by studying the isostructural but fixed-valence compound β-LuAlB4. Quantum oscillation measurements and density functional theory calculations reveal a Fermi surface in β-LuAlB4 markedly different from that of β-YbAlB4, consistent with a "large"Fermi surface in the latter. We also find an unexpected in-plane anisotropy of the electronic structure, in contrast to the isotropic Kondo hybridization in β-YbAlB4.

    DOI： 10.1103/PhysRevB.102.081102

  • Strong in-plane anisotropy in the electronic structure of fixed-valence beta-LuAlB4 Reviewed

    P. Reiss **, J. Baglo **, H. Tan **, X. Chen **, S. Friedemann **, Kentaro Kuga, F. M. Grosche **, S. Nakatsuji **, M. Sutherland **

    PHYSICAL REVIEW B   102 ( 8 )   081102-1 - 08112-6   2020.8

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  • Observation of Electronic Structures in Sr-Based Iridates by Bulk-Sensitive Photoemission Spectroscopy Reviewed

    Koya Nakagawa, Hidenori Fujiwara, Satoru Hamamoto, Sho Miyazaki, Yasuhiro Nakatani, Kentaro Kuga, Atsushi Higashiya, Toshiharu Kadono, Kenji Tamasaku, Makina Yabashi, Tetsuya Ishikawa, Takayuki Muro, Shin Imada, Akira Sekiyama, Kouichi Takase, Hiromi Kobori, Atsushi Yamasaki

    Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019)   30   011146-1 - 6   2020.3

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    Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Journal of the Physical Society of Japan  

    DOI： 10.7566/jpscp.30.011146

  • Ground State Local 4f Symmetry of CeAgSb2 Probed by Linearly Polarized Hard X-ray Photoemission Reviewed

    H. Fujiwara, Y. Kondo, S. Hamamoto, Y. Kanai-Nakata, K. Kuga, A. Yamasaki, A. Higashiya, T. Kadono, S. Imada, T. Kiss, A. Tanaka, K. Tamasaku, M. Yabashi, T. Ishikawa, T. Ebihara, A. Sekiyama

    Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019)   2020.3

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    DOI： 10.7566/jpscp.30.011101

  • Local 4f Electronic Structure in PrAg2In Studied by Polarized X-Ray Absorption and Photoemission Spectroscopy Reviewed

    Satoru Hamamoto, Shuhei Fujioka, Yuina Kanai-Nakata, Kohei Yamagami, Kentaro Kuga, Hidenori Fujiwara, Takayuki Kiss, Hiroyuki S. Suzuki, Atsushi Higashiya, Atsushi Yamasaki, Shin Imada, Arata Tanaka, Yukiharu Takeda, Yuji Saitoh, Kenji Tamasaku, Makina Yabashi, Tetsuya Ishikawa, Akira Sekiyama

    Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019)   30   011113-1 - 5   2020.3

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    DOI： 10.7566/jpscp.30.011113

  • Linearly Polarized Hard X-Ray Photoemission Spectroscopy of PrBe13 Reviewed

    Satoru Hamamoto, Yuina Kanai-Nakata, Hidenori Fujiwara, Kentaro Kuga, Takayuki Kiss, Atsushi Higashiya, Atsushi Yamasaki, Shin Imada, Arata Tanaka, Kenji Tamasaku, Makina Yabashi, Tetsuya Ishikawa, Hiroyuki Hidaka, Tatsuya Yanagisawa, Hiroshi Amitsuka, Akira Sekiyama

    Proceedings of J-Physics 2019: International Conference on Multipole Physics and Related Phenomena   29   012010-1 - 6   2020.2

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    Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Journal of the Physical Society of Japan  

    DOI： 10.7566/jpscp.29.012010

  • Linear polarization-dependent core-level photoemission spectroscopy in Yb-based valence fluctuating system Reviewed

    Kentaro Kuga, Yuina Kanai, Hidenori Fujiwara, Kohei Yamagami, Satoru Hamamoto, Yuichi Aoyama, Akira Sekiyama, Atsushi Higashiya, Toshiharu Kadono, Shin Imada, Atsushi Yamasaki, Kenji Tamasaku, Makina Yabashi, Tetsuya Ishikawa, Satoru Nakatsuji, Takayuki Kiss

    Journal of Electron Spectroscopy and Related Phenomena   238   146889-1 - 4   2020.1 （   ISSN:0368-2048   eISSN:1873-2526 ）

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    Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER  

    © 2019 In this paper, we show the linearly polarized hard X-ray core-level photoemission spectroscopy of valence fluctuating system β-YbAlB4. Interestingly, we observed subtle but distinct linear dichroisms in Yb2+ 3d5/2 core-level spectra at several angles of β-YbAlB4. Basically linear dichroism in Yb2+ 3d5/2 core-level spectrum is not expected in the ionic picture because Yb2+ 4f orbital is fully occupied. These contradiction indicates the breakdown of ionic picture in β-YbAlB4.

    DOI： 10.1016/j.elspec.2019.08.004

  • Observation of the 4f ground-state symmetry in strongly correlated cubic Pr compounds probed by linearly polarized 3d core-level photoemission spectroscopy Reviewed

    S. Hamamoto, Y. Kanai, S. Fujioka, Y. Nakatani, H. Fujiwara, K. Kuga, T. Kiss, A. Higashiya, A. Yamasaki, S. Imada, A. Tanaka, K. Tamasaku, M. Yabashi, T. Ishikawa, H. Hidaka, T. Yanagisawa, H. Amitsuka, K. T. Matsumoto, T. Onimaru, T. Takabatake, A. Sekiyama

    Journal of Electron Spectroscopy and Related Phenomena   238   146885-1 - 4   2020.1 （   ISSN:0368-2048 ）

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    © 2019 Elsevier B.V. We report the core-level photoemission study of cubic PrBe13, PrIr2Zn20 and PrB6 using linearly polarized hard X-ray. We have successfully observed linear dichroism (LD) in Pr3+ 3d core-level photoemission spectra reflecting the 4f ground-state symmetry for all the compounds. The observed LDs and polarization-dependent spectra are reproduced by ionic-model calculations including the full multiplet theory and the local crystalline electric field (CEF) splitting. We have confirmed that LDs in Pr3+ 3d core-level photoemission spectra are able to determine unambiguously the Pr3+ 4f ground-state symmetry.

    DOI： 10.1016/j.elspec.2019.07.006

  • Effect of Anisotropic Hybridization in YbAlB4 Probed by Linear Dichroism in Core-Level Hard X-Ray Photoemission Spectroscopy Reviewed

    Kentaro Kuga, Yuina Kanai, Hidenori Fujiwara, Kohei Yamagami, Satoru Hamamoto, Yuichi Aoyama, Akira Sekiyama, Atsushi Higashiya, Toshiharu Kadono, Shin Imada, Atsushi Yamasaki, Arata Tanaka, Kenji Tamasaku, Makina Yabashi, Tetsuya Ishikawa, Satoru Nakatsuji, Takayuki Kiss

    Physical Review Letters   123 ( 3 )   036404 - 036404   2019.7 （   ISSN:0031-9007   eISSN:1079-7114 ）

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    © 2019 American Physical Society. We have probed the crystalline electric-field ground states of pure |J=7/2,Jz=±5/2 © as well as the anisotropic c-f hybridization in both valence fluctuating systems α- and β-YbAlB4 by linear polarization dependence of angle-resolved core level photoemission spectroscopy. Interestingly, the small but distinct difference between α- and β-YbAlB4 was found in the polar angle dependence of linear dichroism, indicating the difference in the anisotropy of c-f hybridization, which may be a key to understanding a heavy Fermi liquid state in α-YbAlB4 and a quantum critical state in β-YbAlB4.

    DOI： 10.1103/PhysRevLett.123.036404

  • Revising the 4f symmetry in CeCu2Ge2: Soft x-ray absorption and hard x-ray photoemission spectroscopy Reviewed

    H. Aratani, Y. Nakatani, H. Fujiwara, M. Kawada, Y. Kanai, K. Yamagami, S. Fujioka, S. Hamamoto, K. Kuga, T. Kiss, A. Yamasaki, A. Higashiya, T. Kadono, S. Imada, A. Tanaka, K. Tamasaku, M. Yabashi, T. Ishikawa, A. Yasui, Y. Saitoh, Y. Narumi, K. Kindo, T. Ebihara, A. Sekiyama

    Physical Review B   98 ( 12 )   121113\_1 - 121113\_6   2018.9 （   ISSN:2469-9950   eISSN:2469-9969 ）

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    © 2018 American Physical Society. We present a detailed study on the 4f ground-state symmetry of the pressure-induced superconductor CeCu2Ge2 probed by soft x-ray absorption and hard x-ray photoemission spectroscopy. The revised Ce 4f ground states are determined as |Γ7)=0.45|Jz=±52)-0.55| 32) with Σ-type in-plane rotational symmetry. This gives an in-plane magnetic moment consistent with the antiferromagnetic moment as reported in neutron measurements. Since the in-plane symmetry is the same as that for the superconductor CeCu2Si2, we propose that the charge distribution along the c axis plays an essential role in driving the system into a superconducting phase.

    DOI： 10.1103/PhysRevB.98.121113

  • Valence fluctuating compound α-YbAlB<inf>4</inf> studied by 174Yb Mössbauer spectroscopy and X-ray diffraction using synchrotron radiation Reviewed

    Momoko Oura, Shugo Ikeda, Ryo Masuda, Yasuhiro Kobayashi, Makoto Seto, Yoshitaka Yoda, Naohisa Hirao, Saori I. Kawaguchi, Yasuo Ohishi, Shintaro Suzuki, Kentaro Kuga, Satoru Nakatsuji, Hisao Kobayashi

    Physica B: Condensed Matter   536 ( 1 )   162 - 164   2018.5 （   ISSN:0921-4526   eISSN:1873-2135 ）

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    © 2017 Elsevier B.V. The structural properties and the Yb 4f electronic state of the valence fluctuating α-YbAlB4 have been investigated by powder X-ray diffraction under pressure and 174Yb Mössbauer spectroscopy with magnetic fields at low temperature, respectively, using synchrotron radiation. Powder X-ray diffraction patterns showed that the crystal structure does not change up to p ∼ 18 GPa at 8 K and the volume decreases smoothly. However, the pressure dependence of the difference in the structure factor between the (060) and (061) diffraction lines changes at ∼ 3.4 GPa, indicating the change of atomic coordination parameters. The 174Yb Mössbauer spectroscopy measurements at 2 K with 10 and 50 kOe suggest that the electrical quadrupole interaction changes by applied magnetic fields.

    DOI： 10.1016/j.physb.2017.09.035

  • Quantum valence criticality in a correlated metal Reviewed International coauthorship

    Kentaro Kuga, Yosuke Matsumoto, Mario Okawa, Shintaro Suzuki, Takahiro Tomita, Keita Sone, Yasuyuki Shimura, Toshiro Sakakibara, Daisuke Nishio-Hamane, Yoshitomo Karaki, Yasutaka Takata, Masaharu Matsunami, Ritsuko Eguchi, Munetaka Taguchi, Ashish Chainani, Shik Shin, Kenji Tamasaku, Yoshinori Nishino, Makina Yabashi, Tetsuya Ishikawa, Satoru Nakatsuji

    Science Advances   4 ( 2 )   eaao3547 - 6   2018.2 （   ISSN:2375-2548   eISSN:2375-2548 ）

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    Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

    Copyright © 2018 The Authors. A valence critical end point existing near the absolute zero provides a unique case for the study of a quantum version of the strong density fluctuation at the Widom line in the supercritical fluids. Although singular charge and orbital dynamics are suggested theoretically to alter the electronic structure significantly, breaking down the standard quasi-particle picture, this has never been confirmed experimentally to date. We provide the first empirical evidence that the proximity to quantum valence criticality leads to a clear breakdown of Fermi liquid behavior. Our detailed study of the mixed valence compound a-YbAlB4 reveals that a small chemical substitution induces a sharp valence crossover, accompanied by a pronounced non-Fermi liquid behavior characterized by a divergent effective mass and unusual T/B scaling in the magnetization.

    DOI： 10.1126/sciadv.aao3547

  • Hole doping effect on the electronic structure of layered oxypnictide LaOMnAs Reviewed

    A. Higashiya, K. Nakagawa, A. Yamasaki, K. Nagai, S. Fujioka, Y. Kanai, K. Yamagami, H. Fujiwara, A. Sekiyama, Amina Abozeed, T. Kadono, S. Imada, K. Kuga, M. Yabashi, K. Tamasaku, T. Ishikawa, S. Toyama, K. Takase

    Journal of Electron Spectroscopy and Related Phenomena   220   58 - 60   2017.10 （   ISSN:0368-2048   eISSN:1873-2526 ）

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    © 2017 Elsevier B.V. Layered oxypnictide LaOMnAs shows an antiferromagnetic insulator-to-ferromagnetic metal transition at room temperature with increasing the defect of LaO layer which induces hole doping into the MnAs layers. In order to reveal the details of the transition, we have performed hard-X-ray photoelectron spectroscopy for the insulating LaOMnAs and metallic (LaO)0.7MnAs. The spectral changes in the valence band, mainly composed of Mn 3d states, Mn 2p core levels, and La 3d core-levels have been observed across the transition. Our results indicated that Mn 3d state was significantly influenced by the defect of LaO layer.

    DOI： 10.1016/j.elspec.2017.01.006

  • Frustrated magnetism in the Heisenberg pyrochlore antiferromagnets AYb2X4 (A=Cd, Mg; X= S, Se) Reviewed

    Tomoya Higo, Kensuke Iritani, Mario Halim, Wataru Higemoto, Takashi U. Ito, Kentaro Kuga, Kenta Kimura, Satoru Nakatsuji

    Physical Review B   95 ( 17 )   174443-1 - 7   2017.5 （   ISSN:2469-9950   eISSN:2469-9969 ）

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    © 2017 American Physical Society. Our polycrystalline sample study on the Yb-based chalcogenide spinels AYb2X4 (A= Cd, Mg; X= S, Se) has revealed frustrated magnetism due to the antiferromagnetically coupled Heisenberg spin on a pyrochlore lattice. The crystal electric field analysis indicates the Yb ground state has nearly Heisenberg spins with a strong quantum character of the ground doublet. All the materials exhibit an antiferromagnetic order at 1.4-1.8 K, much lower temperatures than the antiferromagnetic exchange coupling scale of ∼10K. The magnetic specific heat CM shows a T3 dependence, indicating the gapless feature in the Yb-based chalcogenide spinels. The magnetic entropy change much smaller than R ln 2 below the Néel temperature and the small local magnetic field estimated from the μSR measurements strongly suggest the significantly reduced size of the ordered moment in comparison with the bare moment size 1.33 μB/Yb, supporting strong fluctuations in the commensurate and incommensurate ordered states in CdYb2S4 and MgYb2S4, respectively.

    DOI： 10.1103/PhysRevB.95.174443

  • Anisotropic Thermal Expansion of α-YbAlB<inf>4</inf> Reviewed

    Yosuke Matsumoto, K. Kuga, T. Tomita, R. Küchler, S. Nakatsuji

    Journal of Physics: Conference Series   807 ( 2 )   2017.4 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Physics Publishing  

    Thermal expansion measurements were performed for α-YbAlB4 using powder X-ray diffraction and our high resolution capacitance dilatometry. Highly anisotropic thermal expansion, which is much larger along the c-axis compared to the a- and b-axes, was observed. In addition, high resolution capacitance dilatometry revealed negative thermal expansion appears below 90 K only along the a-axis, not along the c-axis. The observation is consistent with anisotropic hybridization stronger in the ab-plane, suggesting the formation of anisotripic heavy fermion well below the valence fluctuation temperature scale of 200 ∼ 300 K. Furthermore, linear thermal expansion coefficient along the a-axis starts to decrease below 115 K. The characteristic temperature scale of 90 - 115 K may correspond to the crystal electric field excited level. The in-plane negative thermal expansion can be regarded as a development of anisotropic hybridization due to |Jz = ±5/2 > crystal electric field ground states which becomes dominant on cooling below the excited states.

    DOI： 10.1088/1742-6596/807/2/022005

  • Lifetime-broadening-suppressed X-ray absorption spectrum of β-YbAlB4 deduced from Yb 3d → 2p resonant X-ray emission spectroscopy Reviewed

    Naomi Kawamura, Noriko Kanai, Hisashi Hayashi, Yasuhiro H. Matsuda, Masaichiro Mizumaki, Kentaro Kuga, Satoru Nakatsuji, Shinji Watanabe

    Journal of the Physical Society of Japan   86 ( 1 )   014711-1 - 7   2017.1 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    © 2017 The Physical Society of Japan. In this work, the Yb 3d → 2p (Yb Lα1,2) resonant X-ray emission spectrum of β-YbAlB4 was acquired using excitation energies around the Yb L3-edge, at 2K. Subsequently, the lifetime-broadening-suppressed (LBS) X-ray absorption structure (XAS) spectrum was obtained using the SIM-RIXS program. This spectrum was found to exhibit clearly resolved pre-edge and shoulder structures. Resonant La1 emission spectra were well reproduced from LBS-XAS profiles over wide ranges of excitation and emission energies. In contrast, noticeable discrepancies appeared between the experimental and simulated Lα2 emission spectra, suggesting an effect resulting from M4M5O1 Coster-Kronig transitions. LBS-XAS, in conjunction with partial fluorescence yield (PFY) XAS and transmission XAS, determined a value for the Yb valence (v) in β-YbAlB4 of 2.76 ± 0.08 at 2K. Despite this relatively large uncertainty in v, each method provided a consistent variation in valence (Sv) as the temperature was raised from 2 to 280 K: 0.060 ± 0.004 (LBS-XAS), 0.061 ± 0.005 (PFY-XAS) and 0.058 ± 0.007 (transmission XAS). The smaller δv associated with LBS-XAS demonstrates the greater precision of this method.

    DOI： 10.7566/JPSJ.86.014711

  • Pressure-induced magnetic transition exceeding 30 K in the Yb-based heavy-fermion β-YbAlB4 Reviewed

    Takahiro Tomita, Kentaro Kuga, Yoshiya Uwatoko, Satoru Nakatsuji

    Physical Review B   94 ( 24 )   245130-1 - 6   2016.12 （   ISSN:2469-9950   eISSN:2469-9969 ）

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    © 2016 American Physical Society. Measurements of the electric resistivity ρ(T) under pressure up to 8 GPa were performed on high-quality single crystals of the Yb-based heavy-fermion system β-YbAlB4 in the temperature range 2<T<300 K. In the resistivity data, we observed pressure-induced magnetic ordering above the critical pressure Pc∼2 GPa. The clear difference in the phase diagram under pressure using two types of pressure media indicates that the transition temperature may be further enhanced under application of uniaxial pressure. With pressure, this phase-transition temperature TM is enhanced, reaching 32 K at 8 GPa, which is the highest transition temperature so far recorded for the Yb-based heavy-fermion compounds. The power-law exponent α in ρ=ρ0+ATα below TM gradually changes from 3/2 to 5/2 with increasing pressure from 2 to 8 GPa. In contrast, the resistivity exhibits a T-linear behavior in the temperature range 2≤T≤20 K and is insensitive to pressure below Pc. In this pressure regime, the magnetization is also nearly independent of pressure and shows no anomaly above 2 K. Our results indicate that a quantum critical point for β-YbAlB4 is also located near Pc in addition to the strange metal region near the ambient pressure.

    DOI： 10.1103/PhysRevB.94.245130

  • Quantum criticality and inhomogeneous magnetic order in Fe-doped α-YbAlB4 Reviewed

    D. E. MacLaughlin, K. Kuga, Lei Shu, O. O. Bernal, P. C. Ho, S. Nakatsuji, K. Huang, Z. F. Ding, C. Tan, Jian Zhang

    Physical Review B   93 ( 21 )   214421-1 - 8   2016.6 （   ISSN:2469-9950   eISSN:2469-9969 ）

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    © 2016 American Physical Society. The intermediate-valent polymorphs α- and β-YbAlB4 exhibit quantum criticality and other novel properties not usually associated with intermediate valence. Iron doping induces quantum criticality in α-YbAlB4 and magnetic order in both compounds. We report results of muon spin relaxation (μSR) experiments in α-YbAl1-xFexB4, x=0.014 and 0.25. For x=0.014 we find no evidence for magnetic order down to 25 mK. The dynamic muon spin relaxation rate λd exhibits a power-law temperature dependence λd∝T-a, a=0.40(4), in the temperature range 100 mK-2 K, in disagreement with predictions by theories of antiferromagnetic (AFM) or valence quantum critical behavior. For x=0.25, where AFM order develops in the temperature range 7.5-10 K, we find coexistence of meso- or macroscopically segregated paramagnetic and AFM phases, with considerable disorder in the latter down to 2 K.

    DOI： 10.1103/PhysRevB.93.214421

  • Pressure-induced local structural changes in heavy fermion β-YbAlB<inf>4</inf> Reviewed

    Yui Sakaguchi, Shugo Ikeda, Kentaro Kuga, Shintaro Suzuki, Satoru Nakatsuji, Naohisa Hirao, Yasuo Ohishi, Hisao Kobayashi

    Journal of the Physical Society of Japan   85 ( 2 )   023602-1 - 4   2016.2 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    © 2016 The Physical Society of Japan. The structural properties of β-YbAlB4 with an orthorhombic Cmmm symmetry have been investigated by powder X-ray diffraction analysis using synchrotron radiation under high pressure (up to ∼20 GPa) at 7K. Although the refined lattice parameters exhibit no discontinuity and the pressure dependence of the volume was well reproduced by the Murnaghan's equation of state up to ∼20 GPa, detailed analyses of the observed X-ray diffraction patterns reveal local structure changes in B layers at 3.5(2) and 5.8(1) GPa. The changes in the local structure strongly affect the bonding structures in the B layers among the conduction electrons of β-YbAlB4 under pressure at 7K.

    DOI： 10.7566/JPSJ.85.023602

  • High Magnetic Transition Temperature and Semiconductor like Transport Properties of Mn-doped α-YbAlB<inf>4</inf> Reviewed

    S. Suzuki, T. Tomita, Y. Shimura, K. Kuga, Y. Matsumoto, S. Nakatsuji

    Journal of Physics: Conference Series   683 ( 1 )   2016.2 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    © Published under licence by IOP Publishing Ltd. We succeeded in growing single crystals of α-YbAl1-xMnxB4 by the substitution of Mn for the Al site in the intermediate-valence rare-earth heavy fermion system α-YbAlB4. We performed specific heat and resistivity measurement on single crystals of α-YbAl1-xMnxB4 (x = 40). In the specific heat measurement on α-YbAl0.60Mn0.40B4, a sharp peak was observed at magnetic transition temperature TM = 9.7(6) K. The resistivity measurements on x = 0.40 also show a semiconductor-like behavior in the entire temperature range from 2 - 300 K. An inclination change was also observed at 10(1) K in resistivity measurement. These results indicate a magnetic order. The magnetic transition temperature is quite high compared to its temperatures observed in the other Yb-based heavy fermion compounds.

    DOI： 10.1088/1742-6596/683/1/012009

  • Site-selective 11B NMR studies on YbAlB<inf>4</inf> Reviewed

    S. Takano, M. S. Grbic, K. Kimura, M. Yoshida, M. Takigawa, E. C.T.O. Farrell, K. Kuga, S. Nakatsuji, H. Harima

    Journal of Physics: Conference Series   683 ( 1 )   2016.2 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    © Published under licence by IOP Publishing Ltd. β-YbAlB4 is a distinctive heavy fermion superconductor that exhibits unconventional quantum criticality without tuning in a strongly intermediate valence state. In this paper, we report the result of 11B NMR measurements on the single crystals of, β-YbAlB4 and α- YbAlB4, the locally isostructural polymorph of β-YbAlB4. All 11B NMR lines for both samples were successfully assigned to inequivalent crystallographic sites by comparing the experimental results and the ab-initio calculation of the electric field gradient. In both compounds, the anisotropy of the Knight shift exhibits a characteristic radial pattern, indicating approximate axial symmetry of the hybridization between the Yb-4f electrons and the conduction electrons.

    DOI： 10.1088/1742-6596/683/1/012008

  • Quantum Criticality Beneath the Superconducting Dome in β-YbAlB<inf>4</inf> Reviewed

    T. Tomita, K. Kuga, Y. Uwatoko, S. Nakatsuji

    Journal of Physics: Conference Series   683 ( 1 )   2016.2 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    © Published under licence by IOP Publishing Ltd. Yb-based heavy fermion superconductor β-YbAlB4 at 0 K and 0 T at ambient pressure is located near the quantum critical point with strong mixed valiancy. In this type of Yb electron system, we expect that the magnetic order connected to the quantum critical point derives from the applied pressure. We built a pressure-temperature phase diagram for β-YbAlB4 by measuring the electrical resistivity of high quality single crystal at temperatures down to 40 mK under an applied pressure. A strange metal region appeared, showing non-Fermi liquid ρab α T1.5 behavior, which is stable with applied pressure up to 0.4 GPa, even when below the superconducting dome excluded by a magnetic field of 0.1 T. By increasing of pressure above 2.5 GPa, a magnetic order is first generated. Such ambient quantum criticality/superconductivity is unconventional and is detached from the magnetic order.

    DOI： 10.1088/1742-6596/683/1/012007

  • X-ray Absorption Spectroscopy in the Heavy Fermion Compound α-YbAlB4 at High Magnetic Fields Reviewed

    Taku T. Terashima, Yasuhiro H. Matsuda, Kentaro Kuga, Shintaro Suzuki, Yosuke Matsumoto, Satoru Nakatsuji, Akihiro Kondo, Koichi Kindo, Naomi Kawamura, Masaichiro Mizumaki, Toshiya Inami

    Journal of the Physical Society of Japan   84 ( 11 )   114715-1 - 4   2015.11 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    © 2015 The Physical Society of Japan. α-YbAlB4 shows strong valence fluctuation as well as heavy fermion behavior at low temperatures. It has been theoretically suggested that the quantum criticality owing to the valence fluctuation found in Yb ions plays an important role in the peculiar properties of this material. In this work, we measured the X-ray absorption spectra (XAS) and X-ray magnetic circular dichroism (XMCD) at the L3 edge of Yb ions in high magnetic fields of up to 40 T. It is found that the XAS are almost independent of the magnetic field at 2K, which proves that there is no significant valence change in this field range. The XMCD spectrum exhibits a distinct negative peak at the low-energy side of the L3 edge as well as the main positive peak near the white line. The negative XMCD peak is attributed to the quadrupole transition between the 2p and 4f states, and gives us microscopic information on the 4f state. This finding supports the recent theoretical proposal that |Jz = ±5/2 is the ground state of the localized Yb magnetic moment, where Jz is the z-component of the total angular momentum of Yb3+.

    DOI： 10.7566/JPSJ.84.114715

  • Magnetic order in the frustrated ising quasi-one dimensional compound NaCo(acac)<inf>3</inf>·benzene Reviewed

    Yoshitomo Karaki, Kentaro Kuga, Kenta Kimura, Satoru Nakatsuji, Kazuyuki Matsubayashi, Yoshiya Uwatoko

    Journal of the Physical Society of Japan   84 ( 8 )   084708-1 - 5   2015.8 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    ©2015 The Physical Society of Japan. We report the results of susceptibility, magnetization curve, and specific heat measurements on single crystals of NaCo(acac)3·benzene, which forms a triangular lattice on the ab-plane with Ising ferromagnetic chains along the c-axis. We found a long-range order below 62 mK by specific heat measurement, a steplike increase in susceptibility at this temperature, and a plateau of one-third of the full moment in the M-H curve at 20 mK. We also observed a spin relaxation that obeys the Arrhenius law in the ordered state. The existence of a partially disordered antiferromagnetic state is discussed on the basis of the results.

    DOI： 10.7566/JPSJ.84.084708

  • Intact quasiparticles at an unconventional quantum critical point Reviewed

    M. L. Sutherland, E. C.T. O'Farrell, W. H. Toews, J. Dunn, K. Kuga, S. Nakatsuji, Y. Machida, K. Izawa, R. W. Hill

    Physical Review B - Condensed Matter and Materials Physics   92 ( 4 )   2015.7 （   ISSN:1098-0121   eISSN:1550-235X ）

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    © 2015 American Physical Society. ©2015 American Physical Society. We report measurements of in-plane electrical and thermal transport properties in the limit T→0 near the unconventional quantum critical point in the heavy-fermion metal β-YbAlB4. The high Kondo temperature TK≃200 K in this material allows us to probe transport extremely close to the critical point, at unusually small values of T/TK<5×10-4. Here we find that the Wiedemann-Franz law is obeyed at the lowest temperatures, implying that the Landau quasiparticles remain intact in the critical region. At finite temperatures we observe a non-Fermi-liquid T-linear dependence of inelastic-scattering processes to energies lower than those previously accessed. These processes have a weaker temperature dependence than in comparable heavy fermion quantum critical systems, revealing a temperature scale of T∼0.3K which signals a sudden change in the character of the inelastic scattering.

    DOI： 10.1103/PhysRevB.92.041114

  • Conduction electron spin resonance in the α-Yb<inf>1-x</inf>xFe<inf>x</inf>AlB<inf>4</inf> (0≤x ≤0.50) and α-LuAlB<inf>4</inf>compounds Reviewed

    L. M. Holanda, G. G. Lesseux, E. T. Magnavita, R. A. Ribeiro, S. Nakatsuji, K. Kuga, Z. Fisk, S. B. Oseroff, R. R. Urbano, C. Rettori, P. G. Pagliuso

    Journal of Physics Condensed Matter   27 ( 25 )   2015.7 （   ISSN:0953-8984   eISSN:1361-648X ）

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    © 2015 IOP Publishing Ltd. β-YbAlB4has become one of the most studied heavy fermion systems since its discovery due to its remarkable physical properties. This system is the first reported Yb-based heavy-fermion superconductor (HFS) for which the low-T superconducting state emerges from a non-fermi-liquid (NFL) normal state associated with quantum criticality Nakatsuji et al 2008 Nature 4 603. Additionally, it presents a striking and unprecedented electron spin resonance (ESR) signal which behaves as a conduction electron spin resonance (CESR) at high temperatures and acquires features of the Yb3+ local moment ESR at low temperatures. The latter, also named Kondo quasiparticles spin resonance (KQSR), has been defined as a 4f-ce strongly coupled ESR mode that behaves as a local probe of the Kondo quasiparticles in a quantum critical regime, Holanda et al 2011 Phys. Rev. Lett. 107 026402. Interestingly, β-YbAlB4possesses a previously known structural variant, namely the α-YbAlB4, phase which is a paramagnetic Fermi liquid (FL) at low temperatures Macaluso et al 2007 Chem. Mater. 19 1918. However, it has been recently suggested that the α-YbAlB4phase may be tuned to NFL behavior and/or magnetic ordering as the compound is doped with Fe. Here we report ESR studies on the α-Yb1-xxFexAlB4 (0 ≤x ≤0.50) series as well as on the reference compound α-LuAlB4. For all measured samples, the observed ESR signal behaves as a CESR in the entire temperature range (10K≲T≲300K) in clear contrast with what has been observed for β-YbAlB4. This striking result indicates that the proximity to a quantum critical point is crucial to the occurrence of a KQSR signal.

    DOI： 10.1088/0953-8984/27/25/255601

  • Field evolution of quantum critical and heavy fermi-liquid components in the magnetization of the mixed valence compound &amp;β;-YbAlB4 Reviewed

    Yosuke Matsumoto, Kentaro Kuga, Yoshitomo Karaki, Yasuyuki Shimura, Toshiro Sakakibara, Masashi Tokunaga, Koichi Kindo, Satoru Nakatsuji

    Journal of the Physical Society of Japan   84 ( 2 )   024710-1 - 7   2015.2 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    © 2015 The Physical Society of Japan. We present the high-precision magnetization data of the valence fluctuating heavy fermion superconductor ¢-YbAlB4 in a wide temperature range from 0.02 to 320K spanning four orders of magnitude. We made detailed analyses of the T/B scaling of the magnetization, and firmly confirmed the unconventional zero-field quantum criticality (QC) without tuning. We examined other possible scaling relationship such as T/(B - Bc)δ scaling, and confirmed that δ = 1 provides the best quality of the fit with an upper bound on the critical magnetic field |Bc| 0.2mT. We further discuss the heavy Fermi-liquid component of the magnetization after subtracting the QC component estimated based on the T/B scaling. The temperature dependence of the heavy Fermi-liquid component is found very similar to the magnetization of the polymorph α;-YbAlB4. In addition, the heavy Fermi-liquid component is suppressed in the magnetic field above ∼5T as in α;-YbAlB 4. This was also confirmed by the magnetization measurements up to ∼50 T for both α- and β-YbAlB4. Interestingly, the detailed analyses revealed that the only a part of f electrons participates in the zero-field QC and the heavy fermion behavior. We also present a temperature -magnetic field phase diagram of β-YbAlB4 to illustrate how the characteristic temperature and field scales evolves near the QC.

    DOI： 10.7566/JPSJ.84.024710

  • Unconventional Quantum Criticality in β-YbAlB<inf>4</inf> Detached from Its Magnetically Ordered Phase Reviewed

    Takahiro Tomita, Kentaro Kuga, Yoshiya Uwatoko, Piers Coleman, Satoru Nakatsuji

    Physics Procedia   75   482 - 487   2015 （   ISSN:1875-3884   eISSN:1875-3892 ）

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    Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

    © 2015 The Authors. Published by Elsevier B.V. We studied the effect of pressure on the Yb-based heavy-fermion superconductor β-YbAlB4 (Tc=80 mK) near its quantum critical point (QCP) at ambient pressure. Here, the electrical resistivity ρ(T) of the high-quality single crystal (RRR = 300) is measured under hydrostatic pressure P ≃ 2.7 GPa at low temperatures down to 70 mK. The superconducting transition Tc gradually decreases with the application of pressure and disappears near 0.9 GPa. However, the non-Fermi liquid (NFL) behavior is found to be robust over a broad range of pressure 0 ≤ P ≤ 0.5 GPa. The NFL state above Tc gradually changes to the Fermi liquid state with the application of pressure above P ≃ 0.5 GPa. The magnetic order transition is first observed at 50 mK and Pc = 2.7 GPa. The P -T phase diagram indicates that the QCP lying beneath the superconductivity dome is detached from the magnetically ordered phase.

    DOI： 10.1016/j.phpro.2015.12.060

  • Two Magnetic Phases in alpha-YbAl1−xFexB4 Reviewed

    Kentaro Kuga, Shintaro Suzuki, Satoru Nakatsuji

    JPS Conference Proceedings   3   012013-1 - 4   2014.6

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    DOI： 10.7566/JPSCP.3.012013

  • Magnetization of Yb-Based Mixed-Valent Compounds at Megagauss Fields Reviewed

    T. Terashima, Y. H. Matsuda, K. Kuga, Y. Matsumoto, S. Nakatsuji, K. Yoshimura, T. Nakahigashi

    JPS Conference Proceedings   3   011027-1 - 5   2014.6

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    DOI： 10.7566/JPSCP.3.011027

  • Suppression of the Heavy Fermion State in Magnetic Fields in the Mixed Valent alpha-YbAIB4 Reviewed

    Yosuke Matsumoto, Kuga Kentaro, Satoru Nakatsuji

    JPS Conference Proceedings   3   011076-1 - 5   2014.6

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    DOI： 10.7566/JPSCP.3.011076

  • Structural and Magnetic Properties of alpha-Yb(Al1−xFex)B4 under Hydrostatic Pressure Reviewed

    Yui Sakaguchi, Shugo Ikeda, Kentaro Kuga, Satoru Nakatsuji, Naohisa Hirao, Yasuo Ohishi, Hisao Kobayashi

    JPS Conference Proceedings   3   011059-1 - 6   2014.6

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    DOI： 10.7566/JPSCP.3.011059

  • Superconducting Properties of the Ferroquadrupolar Cubic Gamma3 Compound PrTi2Al20 Reviewed

    Akito Sakai, Kentaro Kuga, Satoru Nakatsuji

    JPS Conference Proceedings   3   011066-1 - 6   2014.6

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    DOI： 10.7566/JPSCP.3.011066

  • High pressure measurements of the resistivity of β-YbAlB<inf>4</inf> Reviewed

    T. Tomita, K. Kuga, Y. Uwatoko, S. Nakatsuji

    Journal of Physics: Conference Series   592 ( 1 )   012019-1 - 5   2014 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    The electric resistivity ρ(T) under hydrostatic pressure up to 8 GPa was measured above 2 K using a high-quality single crystal of the Yb-based heavy fermion system β-YbAlB4. We found pressure-induced magnetic ordering above the critical pressure Pc ≈ 2.4 GPa. This phase transition temperature TM is enhanced with pressure and reaches 30 K at a pressure of 8 GPa, which is the highest transition temperature for the Yb-based heavy fermion compounds. In contrast, the resistivity is insensitive to pressure below Pc and exhibits the T-linear behavior in the temperature range between 2 and 20 K. Our results indicate that quantum criticality for β-YbAlB4 is also located near Pc in addition to the ambient pressure.

    DOI： 10.1088/1742-6596/592/1/012019

  • Anisotropic transverse magnetoresistivity in α-YbAlB<inf>4</inf> Reviewed

    Yosuke Matsumoto, Jinpyo Hong, Kentaro Kuga, Satoru Nakatsuji

    Journal of Physics: Conference Series   592 ( 1 )   012086-1 - 6   2014 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    We measured the transverse magnetoresistivity of the mixed valence compound α-YbAlB4. Two configurations were used where current was applied along [110] direction for both and magnetic field was applied along [-110] and c-axis. We found the transverse magnetoresistivity is highly anisotropic. In the weak field below 1 T, it is consistent with stronger c-f hybridization in the ab plane which was suggested from the previous zero field resistivity measurements. At the higher field above 3 T, we observed a negative transverse magnetoresistivity for the field applied along the c-axis. The temperature dependences of the resistivity measured at several different fields suggest the suppression of the heavy fermion behavior at the characteristic field of ∼ 5.5 T.

    DOI： 10.1088/1742-6596/592/1/012086

  • Synchrotron X-ray spectroscopy study on the valence state and magnetization in α-YbAl<inf>1-x</inf>Fe<inf>x</inf>B<inf>4</inf> (x =0.115) at low temperatures and high magnetic fields Reviewed

    T. Terashima, Y. H. Matsuda, K. Kuga, S. Suzuki, Y. Matsumoto, S. Nakatsuji, A. Kondo, K. Kindo, N. Kawamura, M. Mizumaki, T. Inami

    Journal of Physics: Conference Series   592 ( 1 )   012020-1 - 6   2014 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    Valence fluctuation phenomena in rare-earth intermetallic compounds have attracted attention because the quantum criticality of the valence transition has been proposed theoretically. Recently, it was found that β-YbAlB4 shows quantum criticality without tuning and has a strong mixed-valence state. In this study, we measured the magnetization curve and X-ray magnetoabsorption in α-YbAl1-xFexB4 (x= 0.115), which is a locally isostructural polymorph of β-YbAlB4. The magnetization and X-ray experiments were performed in fields up to 55 and 40 T, respectively. A small increase in the Yb valence was observed at fields where the magnetization curve exhibited a change in slope.

    DOI： 10.1088/1742-6596/592/1/012020

  • Magnetic order induced by Fe doping in the intermediate valence system β-YbAlB<inf>4</inf> Reviewed

    K. Kuga, S. Nakatsuji

    Journal of the Korean Physical Society   63 ( 3 )   549 - 550   2013.8 （   ISSN:0374-4884   eISSN:1976-8524 ）

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    Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：KOREAN PHYSICAL SOC  

    We have succeeded in doping Fe at the Al site in the intermediate valence and quantum critical material β-YbAlB4 up to 6%. Our measurements of the magnetization and the specific heat for β-YbAl0.94Fe0.06B4 show magnetic ordering at 10 K. The antiferromagnetic Weiss temperature of 88 K, which is smaller than the 110 K for β-YbAlB4, indicates that Fe doping suppresses the Kondo temperature and induces magnetism, driving the system away from the quantum critical point. © 2013 The Korean Physical Society.

    DOI： 10.3938/jkps.63.549

  • Mössbauer spectroscopy of Fe-doped valence-fluctuating α-YbAlB<inf>4</inf> Reviewed

    Yui Sakaguchi, Shugo Ikeda, Hisao Kobayashi, Kentaro Kuga, Keita Sone, Satoru Nakatsuji

    Journal of the Korean Physical Society   62 ( 12 )   2146 - 2149   2013.7 （   ISSN:0374-4884   eISSN:1976-8524 ）

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    The magnetic properties of high-quality ∼25 at.% Fe doped α-YbAlB4 with an orthorhombic Pbam structure were investigated by using magnetization measurements and 57Fe Mössbauer spectroscopy. The temperature dependence of the magnetization along the a-axis showed anomalies at T N2 ∼ 7.7 K and T N1 ∼ 10.4 K. Broadenings of the peaks in the Mössbauer spectrum were observed at temperatures below 6 K, which were due to the magnetic hyperfine fields transferred from the Yb magnetic moments. The evaluated transferred magnetic hyperfine field almost disappears around T N2. The anomalous temperature dependence of the transferred magnetic hyperfine field reveals that the magnetic structure and the ordered magnetic moments of the Yb ions show complex temperature dependences at temperatures below T N1. © 2013 The Korean Physical Society.

    DOI： 10.3938/jkps.62.2146

  • Synchrotron X-ray spectroscopy study on the valence state in α- and β-YbAlB<inf>4</inf> at low temperatures and high magnetic fields Reviewed

    Y. H. Matsuda, T. Nakamura, K. Kuga, S. Nakatsuji, S. Michimura, T. Inami, N. Kawamura, M. Mizumaki

    Journal of the Korean Physical Society   62 ( 12 )   1778 - 1781   2013.7 （   ISSN:0374-4884   eISSN:1976-8524 ）

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    The valence state of Yb ions in β-YbAlB4 and its polymorph α-YbAlB4 has been investigated by using X-ray absorption and emission spectroscopy in SPring-8 at temperatures from 2 to 280 K. The observed Yb valence is 2.78 ± 0.01 in β-YbAlB4 at 2 K by using the X-ray emission spectroscopy. The valence is found to gradually increase with increasing temperature toward the trivalent state, and the characteristic temperature of the valence fluctuation is expected to be about 290 K. We also found a small increase in the Yb valence (∼ 0.002) by applying a magnetic field of 32 T at 40 K to β-YbAlB4. © 2013 The Korean Physical Society.

    DOI： 10.3938/jkps.62.1778

  • Chemical effects of high-resolution yblγ<inf>4</inf> emission spectra: A possible probe for chemical analysis Reviewed

    Hisashi Hayashi, Noriko Kanai, Naomi Kawamura, Yasuhiro H. Matsuda, Kentaro Kuga, Satoru Nakatsuji, Tetsuro Yamashita, Shigeo Ohara

    X-Ray Spectrometry   42 ( 6 )   450 - 455   2013 （   ISSN:0049-8246   eISSN:1097-4539 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

    An 'eccentric' X-ray emission, YbLγ4, was measured for Yb metal, Yb2O3, YbF3, β-YbAlB4, YbNi3Al9, and YbNi3Ga9 with a resolution of ~0.9eV. Peak splitting of the YbLγ4 line was observed in all the recorded spectra and was attributed to the two components originating from the LS coupling of the Yb5p hole, the Yb5p1/2 (LIOII: Lγ4′) and Yb5p3/2 components (LIOIII: Lγ4). The spectra were substantially different depending on the chemical environment of Yb. The position of the Lγ4+Lγ4′ band shifts depending on the valence of Yb (v): ~4.4eV from divalent to trivalent. The Lγ4+Lγ4′ spectra of the mixed valence intermetallics, i.e. YbNi3Ga9 (v=2.59) and β-YbAlB4 (v=2.75), were fairly well reproduced by averaging the spectra of divalent Yb and trivalent YbNi3Al9, which suggests the possibility of using the YbLγ4 emission for determining the valence of Yb intermetallics. In trivalent Yb compounds, the relative intensity of Lγ4 compared with that of Lγ4′, as well as the appearance of a high-energy satellite, was found to be influenced by the ligands around the Yb ions. With the aid of preliminary atomic multiplet and band structure calculations, the differences in the valence band structure and resultant screening effects on the OII,III-1 states were determined to be the possible causes for the observed ligand dependence. © 2013 The Authors.

    DOI： 10.1002/xrs.2502

  • Thermoelectric response near a quantum critical point of β-YbAlB <inf>4</inf> and YbRh <inf>2</inf>Si <inf>2</inf>: A comparative study Reviewed

    Y. MacHida, K. Tomokuni, C. Ogura, K. Izawa, K. Kuga, S. Nakatsuji, G. Lapertot, G. Knebel, J. P. Brison, J. Flouquet

    Physical Review Letters   109 ( 15 )   156405-1 - 5   2012.10 （   ISSN:0031-9007   eISSN:1079-7114 ）

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    The thermoelectric coefficients have been measured down to a very low temperature for the Yb-based heavy-fermion compounds β-YbAlB 4 and YbRh 2Si 2, often considered as model systems for the local quantum criticality case. We observe a striking difference in the behavior of the Seebeck coefficient S in the vicinity of their respective quantum critical point (QCP). Approaching the critical field, S/T is enhanced in β-YbAlB 4, but drastically reduced in YbRh 2Si 2. The ratio of thermopower to specific heat remains constant for β-YbAlB 4, but it is significantly reduced near the QCP in YbRh 2Si 2. In both systems, on the other hand, the Nernst coefficient shows a diverging behavior near the QCP. The interplay between valence and magnetic quantum criticality and the additional possibility of a Lifshitz transition crossing the critical field under magnetic field are discussed as the origin of the different behaviors of these compounds. © 2012 American Physical Society.

    DOI： 10.1103/PhysRevLett.109.156405

  • Superconductivity in the ferroquadrupolar state in the quadrupolar kondo lattice PrTi <inf>2</inf>Al <inf>20</inf> Reviewed

    Akito Sakai, Kentaro Kuga, Satoru Nakatsuji

    Journal of the Physical Society of Japan   81 ( 8 )   083702-1 - 4   2012.8 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    The cubic compound PrTi 2Al 20 is a quadrupolar Kondo lattice system that exhibits quadrupolar ordering due to the non-Kramers 3 ground doublet and has strong hybridization between 4f and conduction electrons. Our study using high-purity single crystals reveals that PrTi 2Al 20 exhibits type-II superconductivity at T c = 200mK in the nonmagnetic ferroquadrupolar state. The superconducting critical temperature and field phase diagram indicates clean limit superconductivity with moderately enhanced effective mass of m*=m0 ̃ 16. © 2012 The Physical Society of Japan.

    DOI： 10.1143/JPSJ.81.083702

  • T/B scaling of magnetization in the mixed valent compound β-YbAlB <inf>4</inf> Reviewed

    Yosuke Matsumoto, S. Nakatsuji, K. Kuga, Y. Karaki, Y. Shimura, T. Sakakibara, A. H. Nevidomskyy, P. Coleman

    Journal of Physics: Conference Series   391 ( 1 )   012041-1 - 4   2012 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    Here we provide the first clear evidence of Fermi-liquid breakdown in an intermediate valence system. We employ high precision magnetization measurements of the valence fluctuating superconductor β-YbAlB4 to probe the quantum critical free energy down to temperatures far below the characteristic energy scale of the valence fluctuations. The observed T/B scaling in the magnetization over three decades not only indicates unconventional quantum criticality, but places an upper bound on the critical magnetic field |Bc| < 0.2 mT, a value comparable with the Earth's magnetic field and six orders of magnitude smaller than the valence fluctuation scale. This tiny value of the upper bound on Bc, well inside the superconducting dome, raises the fascinating possibility that valence fluctuating β-YbAlB4 is intrinsically quantum critical, without tuning the magnetic field, pressure, or composition: the first known example of such a phenomenon in a metal. © Published under licence by IOP Publishing Ltd.

    DOI： 10.1088/1742-6596/391/1/012041

  • Anisotropic heavy-Fermi-liquid formation in valence-fluctuating α-YbAlB<inf>4</inf> Reviewed

    Yosuke Matsumoto, Kentaro Kuga, Takahiro Tomita, Yoshitomo Karaki, Satoru Nakatsuji

    Physical Review B - Condensed Matter and Materials Physics   84 ( 12 )   125126-1 - 7   2011.9 （   ISSN:1098-0121   eISSN:1550-235X ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

    α-YbAlB4 is the locally isostructural polymorph of β-YbAlB4, the first example of a Yb-based heavy fermion superconductor that exhibits pronounced non-Fermi-liquid behavior above T c. Interestingly, both α-YbAlB4 and β-YbAlB4 have strongly intermediate valence. Our single-crystal study of the specific heat, magnetization, and resistivity has confirmed the Fermi-liquid ground state of α-YbAlB4 in contrast to the quantum criticality observed in β-YbAlB4. Both systems exhibit Kondo lattice behavior with the characteristic temperature scale T *∼8 K in addition to a valence-fluctuation scale ∼200 K. Below T*, α-YbAlB4 forms a heavy-Fermi-liquid state with an electronic specific heat coefficient γ∼130 mJ/mol K2 and a large Wilson ratio greater than 7, which indicates ferromagnetic correlation between Yb moments. A large anisotropy in the resistivity, which is one of the largest in heavy fermions, suggests that the hybridization between 4f and conduction electrons is much stronger in the ab plane than along the c axis, indicating this is an excellent system to study for revealing the anisotropic hybridization effects. The strongly anisotropic hybridization as well as the large Wilson ratio is the key to understanding the unusual Kondo lattice behavior and heavy-fermion formation in mixed-valence compounds. © 2011 American Physical Society.

    DOI： 10.1103/PhysRevB.84.125126

  • Quantum critical kondo quasiparticles probed by ESR in β-YbAlB <inf>4</inf> Reviewed

    L. M. Holanda, J. M. Vargas, W. Iwamoto, C. Rettori, S. Nakatsuji, K. Kuga, Z. Fisk, S. B. Oseroff, P. G. Pagliuso

    Physical Review Letters   107 ( 2 )   026402-1 - 4   2011.7 （   ISSN:0031-9007   eISSN:1079-7114 ）

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    Electron spin resonance (ESR) can probe conduction electrons (CE) and local moment (LM) spin systems in different materials. A CE spin resonance (CESR) is observed in metallic systems based on light elements or with enhanced Pauli susceptibility. LM ESR can be seen in compounds with paramagnetic ions and localized d or f electrons. Here we report a remarkable and unprecedented ESR signal in the heavy-fermion superconductor β-YbAlB4 which behaves as a CESR at high temperatures and acquires characteristics of the Yb3 LM ESR at low temperature. This dual behavior strikes as an in situ unique observation of the Kondo quasiparticles in a quantum critical regime. The proximity to a quantum critical point may favor the appearance of this dual character of the ESR signal in β-YbAlB4. © 2011 American Physical Society.

    DOI： 10.1103/PhysRevLett.107.026402

  • Anisotropic electrical transport in the heavy fermion compound α-YbAlB<inf>4</inf> Reviewed International coauthorship

    Kentaro Kuga, Yosuke Matsumoto, Naoki Horie, Satoru Nakatsuji

    Journal of the Physical Society of Japan   80 ( SUPPL. A )   SA089-1 - 2   2011.7 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PHYSICAL SOC JAPAN  

    We studied the electrical transport properties of the heavy fermion compound α-YbAlB4, an isostructural polymorph of the Yb-based heavy fermion superconductor β-YbAlB4. The magnetic part of the ab-plane resistivity of α-YbAlB4, ρab, is about four times larger than ρc along the c-axis at 300 K. With decreasing temperature, the ratio ρab/ρc increases and reaches ∼ 9, forming a peak at around 10 K. In contrast, α-LuAlB4 shows almost temperature independent anisotropy ρab/ρc ∼ 3.5. These observations indicate that the hybridization between 4f and conduction electrons is the origin of the enhanced anisotropy in the resistivity of α-YbAlB4 at low temperatures. © 2011 The Physical Society of Japan.

    DOI： 10.1143/JPSJS.80SA.SA089

  • Kondo lattice behavior in the valence fluctuating systems α- and β-YbAlB<inf>4</inf> Reviewed

    Yosuke Matsumoto, Kentaro Kuga, Naoki Horie, Satoru Nakatsuji

    Journal of the Physical Society of Japan   80 ( SUPPL. A )   SA090-1 - 3   2011.7 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PHYSICAL SOC JAPAN  

    We have measured specific heat and magnetization of the Yb-based heavy Fermion systems α-YbAlB4 and β-YbAlB4. α-YbAlB4 is a locally isostructural polymorph of the first example of an Yb-based heavy Fermion superconductor β-YbAlB4, which exhibits pronounced non-Fermi-liquid behavior above the superconducting transition temperature Tc = 80 mK. The results reveal a Fermi liquid ground state for α-YbAlB4 in contrast to the quantum criticality found for β-YbAlB4. Interestingly, both systems exhibit Kondo lattice behavior with its characteristic temperature scale T * ∼ 8 K, despite of their strongly intermediate valence with the temperature scale of ∼ 200 K. We discuss the origin of this unusual behavior, making a comparison with the typical mixed valent compound YbAl 3. Large Wilson ratios indicate the existence of ferromagnetic correlation as a possible origin for the Kondo lattice behavior. © 2011 The Physical Society of Japan.

    DOI： 10.1143/JPSJS.80SA.SA090

  • Low temperature magnetic properties of Pr(Cu,Ga)<inf>13</inf> with orbitally degenerate ground state Reviewed

    Yasuyuki Shimura, Toshiro Sakakibara, Kentaro Kuga, Jung Young Cho, Julia Y. Chan

    Journal of the Physical Society of Japan   80 ( SUPPL. A )   SA072-1 - 3   2011.7 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PHYSICAL SOC JAPAN  

    Magnetic susceptibility χ(T) and the specific heat C(T) of a cubic compound Pr(Cu,Ga)12.85 were measured at low temperatures down to 0.1 K. χ(T) shows Curie-Weiss behavior down to ∼1 K and turns to saturate at lower temperatures. This behavior is best understood by assuming a Γ5 magnetic triplet for the crystalline electric field ground state of Pr3+ (4f2, J = 4). The C(T) data indicate a continuous releasing of the Γ5 entropy below ∼12 K, with no evidence of a phase transition down to 0.1 K. At low temperatures below 0.5 K, a 141Pr nuclear Schottky tail is found to develop in zero field, which can be ascribed to a hyperfine field from the Pr moment. The estimated Pr moment value (1.3 μB) is found to be significantly smaller than the full moment value of 2 μB for the Γ5 triplet, which is interpreted by fluctuating Pr moments in the ground state whose time scale is comparable to the Pr nuclear spin relaxation time. The analysis yields a large C/T value of 2.2 J/mol·K2 at low temperatures below 1 K. © 2011 The Physical Society of Japan.

    DOI： 10.1143/JPSJS.80SA.SA072

  • Thermoelectric coefficients of the quantum critical β-YbAlB <inf>4</inf> Reviewed

    Y. Machida, C. Ogura, K. Izawa, K. Kuga, S. Nakatsuji

    Journal of the Physical Society of Japan   80 ( SUPPL. A )   SA088-1 - 3   2011.7 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PHYSICAL SOC JAPAN  

    We report the low-temperature thermoelectric power S (T) on high-quality single crystals of β-YbAlB4 down to 40 mK. β-YbAlB 4 is the first Yb-based heavy fermion superconductor with the transition temperature of Tc ∼ 80 mK, and stoichiometrically quantum critical at ambient pressure and under zero magnetic field. In the vicinity of a quantum critical point, S (T)/T exhibits a dramatic enhancement and takes large negative values at low temperatures. By contrast, when the system goes into the Fermi liquid state by applying the magnetic field, S (T)/T becomes constant. From the comparative study using the different quality samples, we confirm that the thermoelectric power is a good probe to elucidate the low-energy electronic excitations of the strongly correlated metals. The apparently different behaviors of the dimensionless ratio q of the thermoelectric power S and the specific heat C between β-YbAlB4 and YbRh2Si2 toward the QCP suggest that the systems belong to distinct classes of the quantum criticality. © 2011 The Physical Society of Japan.

    DOI： 10.1143/JPSJS.80SA.SA088

  • Low-temperature magnetic properties of Pr(Cu,Ga)<inf>12.85</inf> Reviewed

    Y. Shimura, T. Sakakibara, K. Kuga, J. Y. Cho, J. Y. Chan

    Journal of Physics: Conference Series   273 ( 1 )   012054-1 - 4   2011 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

    Magnetization of a cubic compound Pr(Cu,Ga)12.85 was examined at low temperatures down to 0.07 K in fields up to 14.5 T. The magnetic susceptibility χ(T) exhibits Curie-Weiss behavior down to 1 K. Field variation of the magnetization M(H) at 0.12 K shows a steep initial rise to 1.3 μB/Pr at 2 T, followed by a gradual increase in higher fields reaching 1.9 μB/Pr at 14.5 T. The results indicate that the crystalline-electric-field ground state of Pr3+ is a Γ5 magnetic triplet. On cooling below 1 K, χ(T) tends to saturate and provides no evidence of a phase transition down to ∼0.3 K, suggesting onsite as well as intersite fluctuations exist. Below 0.25 K, a weak history dependence is observed in χ(T), which can be attributed to a spin-glass-like freezing of the Pr moment. A weak magnetic field of ∼0.2 T suppresses this spin-glass-like state, and non-Fermi liquid like behavior remains in M(T) down to 0.08 K. © Published under licence by IOP Publishing Ltd.

    DOI： 10.1088/1742-6596/273/1/012054

  • Local moment behaviors of the valence fluctuating systems β-YbAlB <inf>4</inf> and α-YbAlB<inf>4</inf> Reviewed

    Y. Matsumoto, K. Kuga, N. Horie, S. Nakatsuji

    Journal of Physics: Conference Series   273 ( 1 )   012006-1 - 4   2011 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

    β-YbAlB4 is the first example of an Yb-based heavy Fermion superconductor with Tc = 80 mK and exhibits pronounced non-Fermi-liquid behavior above Tc. On the other hand, recent hard x-ray photoemission spectroscopy measurements have revealed strong intermediate valence of both β-YbAlB4 and its locally isostructural polymorph α-YbAlB4 . Here we present the results of the specific heat and magnetization measurements of β-YbAlB4 and α-YbAlB4 . The results indicate a Fermi liquid ground state for α-YbAlB4 in contrast to the quantum criticality found in β-YbAlB4 . Interestingly, both systems exhibit Kondo lattice behavior with large Wilson ratio below T* ∼ 8K, through the renormalization of a high valence fluctuation scale ∼ 200 K. © Published under licence by IOP Publishing Ltd.

    DOI： 10.1088/1742-6596/273/1/012006

  • Strong valence fluctuation in the quantum critical heavy fermion superconductor β-YbAlB4: A hard x-ray photoemission study Reviewed

    M. Okawa, M. Matsunami, K. Ishizaka, R. Eguchi, M. Taguchi, A. Chainani, Y. Takata, M. Yabashi, K. Tamasaku, Y. Nishino, T. Ishikawa, K. Kuga, N. Horie, S. Nakatsuji, S. Shin

    Physical Review Letters   104 ( 24 )   247201-1 - 4   2010.6 （   ISSN:0031-9007   eISSN:1079-7114 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

    Electronic structures of the quantum critical superconductor β-YbAlB4 and its polymorph α-YbAlB4 are investigated by using bulk-sensitive hard x-ray photoemission spectroscopy. From the Yb 3d core level spectra, the values of the Yb valence are estimated to be ∼2.73 and ∼2.75 for α- and β-YbAlB4, respectively, thus providing clear evidence for valence fluctuations. The valence band spectra of these compounds also show Yb2 + peaks at the Fermi level. These observations establish an unambiguous case of a strong mixed valence at quantum criticality for the first time among heavy fermion systems, calling for a novel scheme for a quantum critical model beyond the conventional Doniach picture in β-YbAlB4. © 2010 The American Physical Society.

    DOI： 10.1103/PhysRevLett.104.247201

  • Pronounced non-fermi-liquid behavior of the quantum critical heavy fermion superconductor β-YbAlB<inf>4</inf> Reviewed

    Satoru Nakatsuji, Kentaro Kuga, Takahiro Tomita, Yosuke Matsumoto

    Physica Status Solidi (B) Basic Research   247 ( 3 )   485 - 489   2010.3 （   ISSN:0370-1972   eISSN:1521-3951 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

    Quantum criticality has been a central subject in the study of heavy fermion systems, partly because of the emergence of nontrivial collective phenomena near criticality such as unconventional superconductivity and non-Fermi-liquid behavior. While a number of heavy fermion systems have been studied in Ce(4f*) based compounds, examples of quantum critical materials are still scarce in their hole analogs, namely Yb(4f*) based heavy fermion systems. Here we review the low temperature transport and thermodynamic properties hitherto found for the Yb based heavy fermion superconductor β-YbAlB4 (Tc, = 80mK). The observations indicate that it provides a rare example of a pure metal that displays quantum critical behavior. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI： 10.1002/pssb.200983080

  • Low-temperature magnetization of the quantum critical heavy fermion superconductor β-YbAlB<inf>4</inf> Reviewed

    Yosuke Matsumoto, Kentaro Kuga, Yoshitomo Karaki, Takahiro Tomita, Satoru Nakatsuji

    Physica Status Solidi (B) Basic Research   247 ( 3 )   720 - 722   2010.3 （   ISSN:0370-1972   eISSN:1521-3951 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

    β-YbAlB4 is the first Yb-based heavy fermion superconductor with Tc=80 mK. We measured low-temperature magnetization of high-purity single crystals down to T=25 mK. The measurements have revealed a considerable amount of volume fractions of the superconductivity and the upper critical fieldBc2 curve under field along the c-axis, consistent with the previous results. In the normal state, the previously observed divergent behavior in the temperature dependence of the magnetization has been confirmed using higher-quality samples and under a low field of 22 mT. In addition, the measurements have revealed a power law behavior, namely, dM=dT/T*, which has a slightly higher exponent than the previous results. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI： 10.1002/pssb.200983057

  • Possible multiple gap superconductivity with line nodes in heavily hole-doped superconductor KFe <inf>2</inf>As <inf>2</inf> studied by <inf>75</inf>As nuclear quadrupole resonance and specific heat Reviewed

    Hideto Fukazawa, Yuji Yamada, Kenji Kondo, Taku Saito, Yoh Kohori, Kentarou Kuga, Yosuke Matsumoto, Satoru Nakatsuji, Hijiri Kito, Parasharam M. Shirage, Kunihiro Kihou, Nao Takeshita, Chul Ho Lee, Akira Iyo, Hiroshi Eisaki

    Journal of the Physical Society of Japan   78 ( 8 )   083712-1 - 4   2009.8 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

    We report the 75As nuclear quadrupole resonance (NQR) and specific heat measurements of the heavily hole-doped superconductor KFe 2As 2 (superconducting transition temperature T c 3.5 K). The spin-lattice relaxation rate 1/T 1 in the superconducting state exhibits a gradual temperature dependence with no coherence peak below T c. The quasiparticle specific heat C qp/T shows a small jump, which is about 30% of the electronic specific heat coefficient just below T c. The C qp/T suggests the existence of low-energy quasiparticle excitation at the lowest measurement temperature T - 0.4 K T c/10. The T dependences of 1/T 1 and C qp/T can be explained by a multiple nodal superconducting gap scenario rather than by a multiple fully gapped s ±-wave scenario determined using simple gap analysis. © 2009 The Physical Society of Japan.

    DOI： 10.1143/JPSJ.78.083712

  • Role of f electrons in the fermi surface of the heavy fermion superconductor β-YbAlB4 Reviewed

    E. C.T. O'Farrell, D. A. Tompsett, S. E. Sebastian, N. Harrison, C. Capan, L. Balicas, K. Kuga, A. Matsuo, K. Kindo, M. Tokunaga, S. Nakatsuji, G. Csányi, Z. Fisk, M. L. Sutherland

    Physical Review Letters   102 ( 21 )   216402-1 - 4   2009.5 （   ISSN:0031-9007   eISSN:1079-7114 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

    We present a detailed quantum oscillation study of the Fermi surface of the recently discovered Yb-based heavy fermion superconductor β-YbAlB4. We compare the data, obtained at fields from 10 to 45 T, to band structure calculations performed using the local density approximation. Analysis of the data suggests that f holes participate in the Fermi surface up to the highest magnetic fields studied. We comment on the significance of these findings for the unconventional superconducting properties of this material. © 2009 The American Physical Society.

    DOI： 10.1103/PhysRevLett.102.216402

  • Crystal growth, transport, and magnetic properties of YbCoGa <inf>5</inf> Reviewed

    Edem K. Okudzeto, Kentarou Kuga, Satoru Nakatsuji, Julia Y. Chan

    Crystal Growth and Design   9 ( 4 )   1956 - 1959   2009.4 （   ISSN:1528-7483   eISSN:1528-7505 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

    Single crystals of YbCoGa 5 have been synthesized using gallium flux. YbCoGa 5 crystallizes in the HoCoGa 5 structure type with space group P4/mmm (No. 123), Z = 1 and lattice parameters a = 4.190(1) Å, c = 6.727(3) Å, and V = 118.10(7) Å 3. The cell volume obtained from single crystal X-ray diffraction data shows a larger volume than expected for a Yb 3+ compound. Magnetic susceptibility measurements on single crystals of YbCoGa 5 display temperature independent Pauli paramagnetic behavior. Electrical resistivity measurements of YbCoGa 5 display metallic behavior with a residual resistivity ratio (RRR) of 150 indicating the high crystal quality. © 2009 American Chemical Society.

    DOI： 10.1021/cg801266q

  • Superconducting properties of the non-fermi-liquid system β-YbAlB4 Reviewed

    K. Kuga, Y. Karaki, Y. Matsumoto, Y. Machida, S. Nakatsuji

    Physical Review Letters   101 ( 13 )   137004-1 - 4   2008.9 （   ISSN:0031-9007   eISSN:1079-7114 ）

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    Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

    β-YbAlB4 is the first Yb-based heavy fermion superconductor with Tc=80mK. Our study using high-purity single crystals reveals that strongly type-II heavy fermion superconductivity emerges from the non-Fermi-liquid state with enhanced ferromagnetic fluctuations. High sensitivity of Tc to sample purity indicates strong pair-breaking effects due to impurities, probably of nonmagnetic type, suggesting an unconventional character of the superconductivity. © 2008 The American Physical Society.

    DOI： 10.1103/PhysRevLett.101.137004

  • Crystal structure and physical properties of polymorphs of LnAlB <inf>4</inf> (Ln = Yb, Lu) Reviewed

    Robin T. Macaluso, Satoru Nakatsuji, Kentaro Kuga, Evan Lyle Thomas, Yo Machida, Yoshiteru Maeno, Zachary Fisk, Julia Y. Chan

    Chemistry of Materials   19 ( 8 )   1918 - 1922   2007.4 （   ISSN:0897-4756 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

    Single crystals of YbAlB4 were grown in excess Al flux. Plate- and needle-shaped crystals were found. The plates are found to be ß-YbAlB4, which crystallizes with the ThMoB4 structure type in space group Cmmm (No. 65), Z = 4, with lattice parameters of a = 7.3080(4), b = 9.3150(5), and c = 3.4980(2) Å. The needle-shaped crystals were identified as the first form of YbAlB4 which crystallizes with the YCrB4 structure type in space group Pbam (No. 55), Z = 4, with lattice parameters of a = 5.9220(2), b = 11.4730(3), and c = 3.5060(5) Å. While both compounds have heavy fermion ground states with Isinglike magnetic anisotropy, the electronic specific heat coefficients (γ) differ. The ß-phase has a γ value near 300 mJ mol -1 K-2, more than twice that of the α-phase, γ = 130 mJ mol-1 K-2. A comparison of the structures and physical properties of both polymorphs is presented. © 2007 American Chemical Society.

    DOI： 10.1021/cm062244+

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MISC

  • Probing Yb 5d electronic structures in valence fluctuating α-Yb(Al1-xFex)B4 using HERFD-XAFS

    鳥井優杜, 藤原秀紀, 野末悟郎, 久我健太郎, 河村直己, 東晃太朗, 三村功次郎, 関山明

    日本物理学会講演概要集(CD-ROM)   78 ( 2 )   2023 （   ISSN:2189-079X ）

  • Verification of the Wedemann-Franz law in Yb3Si5 single crystals

    横井滉平, 吉川利輝, 久我健太郎, 松波雅治, 竹内恒博, 町田洋

    日本物理学会講演概要集(CD-ROM)   78 ( 2 )   2023 （   ISSN:2189-079X ）

  • Physical properties of Yb3Si5 clean single crystal

    久我健太郎, 松波雅治, 磯前貴央, 中辻知, 竹内恒博

    日本物理学会講演概要集(CD-ROM)   78 ( 2 )   2023 （   ISSN:2189-079X ）

  • Electronic structure of half-metallic Heusler alloy Mn2VAl probed by soft x-ray angle-resolved photoemission spectroscopy

    堤美和, 堤美和, 藤原秀紀, 藤原秀紀, 野末悟郎, 野末悟郎, 浜本諭, 臼井大智, 臼井大智, 今田真, 今田真, 久我健太郎, 木須孝幸, 木須孝幸, 大浦正樹, 梅津理恵, 関山明, 関山明

    日本物理学会講演概要集(CD-ROM)   78 ( 2 )   2023 （   ISSN:2189-079X ）

  • 共鳴硬X線光電子分光による価数揺動系物質α-Yb(Al1-xFex)B4の電子構造解析

    西岡拓真, 久我健太郎, 藤原秀紀, 姫野良介, 笠原理加, 浜本諭, 西本幸平, 木須孝幸, 保井晃, 雀部矩正, 河村直己, 池永英司, 水牧仁一朗, 筒井智嗣, 三村功次郎, 関山明

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   35th   2022

  • Strong violation of Wiedemann-Franz law in Yb3Si5 single crystal

    久我健太郎, 松波雅治, 松波雅治, 竹内恒博, 竹内恒博

    日本物理学会講演概要集(CD-ROM)   77 ( 2 )   2022 （   ISSN:2189-079X ）

  • Resonant hard X-ray photoemission on valence fluctuating system α-Yb(Al1-xFex)B4

    西岡拓真, 久我健太郎, 藤原秀紀, 姫野良介, 笠原理加, 浜本諭, 西本幸平, 木須孝幸, 保井晃, 雀部矩正, 河村直己, 池永英司, 水牧仁一朗, 筒井智嗣, 三村功次郎, 関山明

    日本物理学会講演概要集(CD-ROM)   77 ( 1 )   2022 （   ISSN:2189-079X ）

  • Mn 2p-3d Resonant Photoemission on half-metallic Heusler alloy Mn2VAl

    堤美和, 堤美和, 藤原秀紀, 藤原秀紀, 野末悟郎, 野末悟郎, 浜本諭, 臼井大智, 臼井大智, 今田真, 今田真, 久我健太郎, 木須孝幸, 木須孝幸, 大浦正樹, 梅津理恵, 関山明, 関山明

    日本物理学会講演概要集(CD-ROM)   77 ( 2 )   2022 （   ISSN:2189-079X ）

  • 174Yb Moessbauer Measurements of valence fluctuations compounds α-YbAl1-xFexB4 in magnetic applied fields: II

    黒澤知樹, 永澤延元, 池田修悟, 増田亮, 瀬戸誠, 依田芳卓, 高橋直樹, 伊賀文俊, 鈴木慎太郎, 久我健太郎, 中辻知, 小林寿夫

    日本物理学会講演概要集(CD-ROM)   77 ( 1 )   2022 （   ISSN:2189-079X ）

  • Giant Peltier coefficient in valence fluctuating material YbSi2

    久我健太郎, 松波雅治, 濱本諭, 大浦正樹, 藤原秀紀, 野末悟郎, 尾瀬朱音, 保井晃, 竹内恒博

    日本物理学会講演概要集(CD-ROM)   77 ( 1 )   2022 （   ISSN:2189-079X ）

  • Study of the ground states of Yb ions in valence fluctuations compounds α-YbAl1-xFexB4

    黒澤知樹, 永澤延元, 池田修悟, 増田亮, 瀬戸誠, 依田芳卓, 高橋直樹, 伊賀文俊, 鈴木慎太郎, 久我健太郎, 中辻知, 小林寿夫

    日本物理学会講演概要集(CD-ROM)   76 ( 1 )   2021 （   ISSN:2189-079X ）

  • Electronic structure of valence fluctuating and quantum critical material α-YbAl1-xFexB4 probed by resonant hard x-ray photoemission spectroscopy

    久我健太郎, 姫野良介, 藤原秀紀, 濱本諭, 保井晃, 雀部矩正, 柴垣善則, 河村直己, 池永英司, 水牧仁一朗, 筒井智嗣, 木須孝幸, 関山明, 三村功次郎, 松波雅治, 竹内恒博

    日本物理学会講演概要集(CD-ROM)   76 ( 1 )   2021 （   ISSN:2189-079X ）

  • Quasi-one-dimensional thermoelectric property in valence fluctuating material α-YbAlB4

    久我健太郎, 中辻知, 中辻知, 松波雅治, 竹内恒博

    日本物理学会講演概要集(CD-ROM)   76 ( 2 )   2021 （   ISSN:2189-079X ）

  • 174Yb Moessbauer measurements of valence fluctuations compounds α-YbAl1-xFexB4 in applied magnetic fields

    黒澤知樹, 永澤延元, 永澤延元, 池田修悟, 増田亮, 瀬戸誠, 依田芳卓, 高橋直樹, 伊賀文俊, 鈴木慎太郎, 久我健太郎, 中辻知, 小林寿夫

    日本物理学会講演概要集(CD-ROM)   76 ( 2 )   2021 （   ISSN:2189-079X ）

  • 重い電子系Yb化合物の熱電特性制御

    岡田真由子, 尾川史武, 久我健太郎, 松波雅治, 竹内恒博

    日本金属学会講演大会(Web)   168th   2021

  • 立方晶Pr化合物の内殻光電子線二色性による4f軌道対称性の決定

    浜本諭, 浜本諭, 中田惟奈, 中田惟奈, 久我健太郎, 藤原秀紀, 藤原秀紀, 木須孝幸, 木須孝幸, 東谷篤志, 東谷篤志, 山崎篤志, 山崎篤志, 今田真, 今田真, 田中新, 玉作賢治, 矢橋牧名, 石川哲也, 日高宏之, 柳澤達也, 網塚浩, 松本圭介, 鬼丸孝博, 高畠敏郎, 関山明, 関山明

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   33rd   2020

  • 内殻光電子スペクトル線二色性による量子臨界物質α-YbAl1-xFexB4の4f軌道対称性決定

    久我健太郎, 中田惟奈, 中田惟奈, 藤原秀紀, 藤原秀紀, 山神光平, 山神光平, 濱本諭, 濱本諭, 青山雄一, 青山雄一, 関山明, 関山明, 東谷篤志, 東谷篤志, 門野利治, 門野利治, 今田真, 今田真, 山崎篤志, 山崎篤志, 田中新, 玉作賢治, 矢橋牧名, 石川哲也, 中辻知, 中辻知, 木須孝幸, 木須孝幸

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   33rd   2020

  • 共鳴硬X線光電子分光による価数揺動系物質β-YbAlB4およびα-YbAlB4の電子構造研究

    姫野良介, 久我健太郎, 藤原秀紀, 浜本諭, 保井晃, 雀部矩正, 柴垣善則, 河村直己, 池永英司, 水牧仁一朗, 筒井智嗣, 木須孝幸, 三村功次郎, 関山明

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   33rd   2020

  • Quantum valence criticality probed by HAXPES and physical property measurements

    久我健太郎, 松本洋介, 大川万里生, 中辻知

    放射光   33 ( 1 )   2 - 9   2020 （   ISSN:0914-9287 ）

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    Language：Japanese  

  • 不均一価数揺動を示すYb化合物の光電子分光

    松波雅治, 久我健太郎, 飯塚拓也, 竹内恒博

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   33rd   2020

  • Thermoelectric Properties and Electronic Structure for CePd3 and Related Materials

    尾川史武, 久我健太郎, 松波雅治, 竹内恒博

    日本物理学会講演概要集(CD-ROM)   75 ( 1 )   1904 - 1904   2020 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    Language：Japanese   Publisher：The Physical Society of Japan  

    DOI： 10.11316/jpsgaiyo.75.1.0_1904

  • Electronic structure of the quantum critical material beta-YbAlB4 probed by resonant hard x-ray photoemission spectroscopy

    Himeno R., Kuga K., Fujiwara H., Hamamoto S., Yasui A., Sasabe N., Sibagaki Y., Kawamura N., Ikenaga E., Mizumaki M., Tsutsui S., Kiss T., Mimura K., Sekiyama A.

    Meeting Abstracts of the Physical Society of Japan   74 ( 2 )   1902 - 1902   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.2.0_1902

  • Crystalline Electric Field Ground State and Effect of Anisotropic Hybridization in YbAlB4 Probed by Linear Dichroism in Core-Level Hard X-ray Photoemission Spectroscopy

    Kuga K., Kanai Y., Fujiwara H., Yamagami K., Hamamoto S., Aoyama Y., Sekiyama A., Higashiya A., Kadono T., Imada S., Yamasaki A., Tanaka A., Tamasaku K., Yabashi M., Ishikawa T., Nakatsuji S., Kiss T.

    Meeting Abstracts of the Physical Society of Japan   74 ( 1 )   2221 - 2221   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.1.0_2221

  • Electronic structure of half-metallic Heusler alloy Co2MnSi probed by linear polarized hard x-ray photoemission spectroscopy

    Nishimoto K., Fujiwara H., Kanai-Nakata Y., Hamamoto S., Kuga K., Kiss T., Kadono T., Imada S., Higashiya A., Yamasaki A., Tamasaku K., Yabashi M., Ishikawa T., Suga S., Umetsu R. Y., Sekiyama A.

    Meeting Abstracts of the Physical Society of Japan   74 ( 2 )   1240 - 1240   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.2.0_1240

  • Determination of the ground-state 4f symmetry of YbNi2Ge2 by linear dichroism in angle resolved core-level photoemission spectroscopy

    Kashiuchi T., Kanai Y., Hamamoto S., Fujiwara H., Kuga K., Kiss T., Higashiya A., Yamasaki A., Imada S., Tanaka A., Tamasaku K., Yabashi M., Ishikawa T., Ebihara T., Sekiyama A.

    Meeting Abstracts of the Physical Society of Japan   74 ( 1 )   1994 - 1994   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.1.0_1994

  • 角度分解内殻光電子線二色性を用いた価数揺動物質YbNi2Ge2における4f基底状態対称性の決定

    樫内利幸, 樫内利幸, 金井惟奈, 金井惟奈, 濱本諭, 濱本諭, 藤原秀紀, 藤原秀紀, 久我健太郎, 木須孝幸, 木須孝幸, 東谷篤志, 東谷篤志, 山崎篤志, 山崎篤志, 門野利治, 門野利治, 今田真, 今田真, 田中新, 玉作賢治, 矢橋牧名, 石川哲也, 海老原孝雄, 関山明, 関山明

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   32nd   2019

  • 軟X線光電子分光による量子臨界物質YbCo2Ge4の電子状態分析

    久我健太郎, 濱本諭, 濱本諭, 中谷泰博, 中谷泰博, 大浦正樹, 北川健太郎, 木須孝幸, 木須孝幸

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   32nd   2019

  • 立方晶PrB6におけるPr4f電子状態を反映した磁場中硬X線内殻光電子線二色性の観測

    浜本諭, 浜本諭, 金井惟奈, 金井惟奈, 藤原秀紀, 藤原秀紀, 木須孝幸, 木須孝幸, 久我健太郎, 東谷篤志, 東谷篤志, 山崎篤志, 山崎篤志, 今田真, 今田真, 田中新, 玉作賢治, 矢橋牧名, 石川哲也, 関山明, 関山明

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   32nd   2019

  • Observation of Pr 4f electronic state in incommensurate antiferromagnetic phase of PrB6 probed by linear dichroism in core level photoemission under a magnetic field

    Hamamoto Satoru, Kanai Y., Fujiwara H., Kiss T., Kuga K., Higashiya A., Yamasaki A., Imada S., Tanaka A., Tamasaku K., Yabashi M., Ishikawa T., Sekiyama A.

    Meeting Abstracts of the Physical Society of Japan   74 ( 1 )   2216 - 2216   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.1.0_2216

  • 硬X線光電子分光を用いた希土類化合物CeAgSb2の基底状態における電子状態の解明

    近藤佑宥, 近藤佑宥, 金井惟奈, 金井惟奈, 濱本諭, 濱本諭, 藤原秀紀, 藤原秀紀, 川田萌樹, 川田萌樹, 樫内利幸, 樫内利幸, 高野彩佳, 高野彩佳, 久我健太郎, 木須孝幸, 木須孝幸, 東谷篤志, 東谷篤志, 門野利治, 門野利治, 今田真, 今田真, 田中新, 玉作賢治, 矢橋牧名, 石川哲也, 海老原孝雄, 関山明, 関山明

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   32nd   2019

  • Ground state local 4f symmetry in the tetragonal strongly correlated Ce compounds probed by polarized hard x-ray photoemission spectroscopy

    Fujiwara H., Kondo Y., Hamamoto S., Kawada M., Aratani H., Nakatani Y., Kanai-Nakata Y., Kuga K., Kiss T., Yamasaki A., Higashiya A., Kadono T., Imada S., Tanaka A., Tamasaku K., Yabashi M., Ishikawa T., Yasui A., Saitoh Y., Ebihara T., Sekiyama A.

    Meeting Abstracts of the Physical Society of Japan   74 ( 2 )   1554 - 1554   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.2.0_1554

  • Magnetic circular dichroism of iron in hard X-ray photoemission spectroscopy under a magnetic field

    Kondo Y., Fujiwara H., Hamamoto S., Kanai-Nakata Y., Kawada M., Takano S., Kuga K., Kiss T., Higashiya A., Yamasaki A., Imada M., Tanaka A., Tamasaku K., Yabashi M., Ishikawa T., Sekiyama A.

    Meeting Abstracts of the Physical Society of Japan   74 ( 2 )   1241 - 1241   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.2.0_1241

  • Physical properties of heavy fermion compound α-YbAlB4 at low temperatures with external magnetic fields Ⅱ

    Kitagawa H., Oura M., Ikeda S., Tanaka Y., Tamasaku K., Masuda R., Kobayashi Y., Seto M., Yoda Y., Suzuki S., Kuga K., Nakatsuji S., Kobayashi H.

    Meeting Abstracts of the Physical Society of Japan   74 ( 1 )   1992 - 1992   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.1.0_1992

  • Electronic States of Na-Si Clathrate of Type2 Studied by X-ray Photoemission Spectroscopy

    Ishida T., Terashima D., Kadono T., Fujiwara H., Sekiyama A., Kuga K., Higashiya A., Yamasaki A., Sakamoto K., Kobayashi Y., Chishima M., Kanai Y., Hamamoto S., Nakagawa K., Tamasaku K., Yabashi M., Ishikawa T., Morito H., Imada S.

    Meeting Abstracts of the Physical Society of Japan   74 ( 1 )   1562 - 1562   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.1.0_1562

  • Determination of the 4f ground-state symmetry of a heavy fermion compound CeRu2Si2 by linear dichroism in hard X-ray core-level photoemission spectroscopy

    Kawada M., Nakatani Y., Aratani H., Kanai Y., Hamamoto S., Kondo H., Fujiwara H., Kuga K., Kiss T., Yamasaki A., Tanaka A., Tamasaku K., Yabashi M., Higashiya A., Isikawa T., Kadono T., Imada S., Ōnuki Y., Aoki D., Sekiyama A.

    Meeting Abstracts of the Physical Society of Japan   74 ( 1 )   1961 - 1961   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.1.0_1961

  • Observation of heterogeneous valence fluctuations in Yb5Si3

    Matsunami M., Kuga K., Iizuka T., Takeuchi T.

    Meeting Abstracts of the Physical Society of Japan   74 ( 2 )   1787 - 1787   2019 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.74.2.0_1787

  • Ground- and excited-state 4f-orbital symmetry of cubic CeAl2 observed by linear dichroism in core-level photoemission spectroscopy

    Kanai Yuina, Kuga K., Higashiya A., Kadono T., Imada S., Ebihara T., Sekiyama A., Hamamoto S., Takano S., Fujiwara H., Kiss T., Tanaka A., Tamasaku K., Yabashi M., Ishikawa T.

    Meeting Abstracts of the Physical Society of Japan   73 ( 2 )   1854 - 1854   2018 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.73.2.0_1854

  • Synchrotron radiation based 174Yb Mössbauer spectroscopic study of YbAlB4 under pressure at low temperature

    Kobayashi H., Kuga K., Nakatsuji S., Ohura M., Ikeda S., Masuda R., Kobayashi Y., Seto M., Tamasaku K., Yoda Y., Suzuki S.

    Meeting Abstracts of the Physical Society of Japan   73 ( 1 )   2006 - 2006   2018 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.73.1.0_2006

  • 異常金属相を持つ重い電子系β-YbAlB4における圧力相図の解明

    冨田崇弘, 冨田崇弘, 高橋博樹, 久我健太郎, 上床義也, 中辻知

    KEK Progress Report (Web)   ( 2018-7 )   2018 （   ISSN:1344-6320 ）

  • YbNi2Ge2の4f基底状態軌道対称性を反映した硬X線内殻光電子線二色性の観測

    樫内利幸, 樫内利幸, 金井惟奈, 金井惟奈, 青山雄一, 青山雄一, 濱本諭, 濱本諭, 山神光平, 山神光平, 藤原秀紀, 藤原秀紀, 久我健太郎, 木須孝幸, 木須孝幸, 東谷篤志, 東谷篤志, 山崎篤志, 山崎篤志, 門野利治, 門野利治, 今田真, 今田真, 田中新, 玉作賢治, 矢橋牧名, 石川哲也, 海老原孝雄, 関山明, 関山明

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   31st   2018

  • Observation of Pr 4f electronic state probed by Linear dichroism in core level photoemission of cubic PrB6 under a magnetic field

    Hamamoto Satoru, Tamasaku K., Yabashi M., Ishikawa T., Sekiyama A., Kanai Y., Fujiwara H., Kiss T., Kuga K., Higashiya A., Yamasaki A., Imada S., Tanaka A.

    Meeting Abstracts of the Physical Society of Japan   73 ( 2 )   1846 - 1846   2018 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.73.2.0_1846

  • Observation of 4f electronic orbital symmetry of heavy fermionic superconductor with broken space inversion symmetry CeIrSi3 by linear dichroism in core-level photoemission

    Kadono Toshiharu, Higashiya A., Yamasaki A., Fujiwara H., Sekiyama A., Tamasaku K., Yabashi M., Ishikawa T., Settai R., Imada S., Sakamoto K., Kobayashi Y., Terashima D., Kanai Y., Hamamoto S., Nakagawa K., Kuga K.

    Meeting Abstracts of the Physical Society of Japan   73 ( 1 )   1513 - 1513   2018 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.73.1.0_1513

  • Polarization Dependence in Ce 3d Core-Level Photoemission Spectroscopy of CeRh3B2

    Kobayashi Yoshiyuki, Terashima Daiki, Chishima Masahiro, Hamamoto Satoru, Nakagawa Koya, Tamasaku Kenji, Yabashi Makina, Ishikawa Tetsuya, Sugawara Hitoshi, Imada Shin, Kadono Toshiharu, Sekiyama Akira, Kanai Yuina, Kuga Kentaro, Higashiya Atsushi, Yamasaki Atsushi, Fujiwara Hidenori, Sakamoto Kohei

    Meeting Abstracts of the Physical Society of Japan   73 ( 2 )   1022 - 1022   2018 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.73.2.0_1022

  • Soft X-ray photoemission spectroscopy study of quantum critical material YbCo2Ge4

    Kuga K., Hamamoto S., Nakatani Y., Oura M., Kitagawa K., Kiss T.

    Meeting Abstracts of the Physical Society of Japan   73 ( 2 )   1883 - 1883   2018 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.73.2.0_1883

  • Physical properties of heavy fermion compound α-YbAlB4 at low temperature with magnetic fields

    Oura M., Kuga K., Nakatsuji S., Kobayashi H., Ikeda S., Tanaka Y., Tamasaku K., Masuda R., Kobayashi Y., Seto M., Yoda Y., Suzuki S.

    Meeting Abstracts of the Physical Society of Japan   73 ( 0 )   2136 - 2136   2018 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.73.1.0_2136

  • X線光電子分光法を用いたNa-Siクラスレートの電子状態の研究

    寺島大貴, 寺島大貴, 門野利治, 門野利治, 森本千香子, 森本千香子, 阪本紘平, 阪本紘平, 小林慶行, 小林慶行, 濱本諭, 濱本諭, 金井惟奈, 金井惟奈, 山神光平, 山神光平, 久我健太郎, 東谷篤志, 東谷篤志, 山崎篤志, 山崎篤志, 藤原秀紀, 藤原秀紀, 関山明, 関山明, 玉作賢治, 矢橋牧名, 石川哲也, 森戸春彦, 今田真, 今田真

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   2018 （   ISSN:2189-079X ）

  • 重い電子系化合物α-YbAlB4の低温における磁場下物性

    大浦桃子, 大浦桃子, 池田修悟, 池田修悟, 池田修悟, 田中良和, 玉作賢治, 増田亮, 小林康浩, 瀬戸誠, 依田芳卓, 鈴木慎太郎, 久我健太郎, 中辻知, 小林寿夫, 小林寿夫, 小林寿夫

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   2018 （   ISSN:2189-079X ）

  • Physical properties of heavy fermion compound α-YbAlB4 at low temperature under pressure and magnetic fields Ⅱ

    Oura M., Suzuki S., Kuga K., Nakatsuji S., Kobayashi H., Ikeda S., Masuda R., Kobayashi Y., Seto M., Yoda Y., Hirao N., Kawaguchi S. I., Ohishi Y.

    Meeting Abstracts of the Physical Society of Japan   72 ( 0 )   1735 - 1735   2017 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.72.2.0_1735

  • Linear dichroism of Yb 3d core level photoelectron spectrum in valence fluctuating compound YbAlB4

    Kuga K., Kadono T., Imada S., Yamasaki A., Tamasaku K., Yabashi M., Ishikawa T., Nakatsuji S., Kiss T., Kanai Y., Fujiwara H., Fujioka S., Yamagami K., Hamamoto S., Aoyama Y., Sekiyama A., Higashiya A.

    Meeting Abstracts of the Physical Society of Japan   72 ( 2 )   1734 - 1734   2017 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.72.2.0_1734

  • 重い電子系化合物α-YbAlB4の低温における圧力・磁場下物性

    大浦桃子, 池田修悟, 池田修悟, 増田亮, 小林康浩, 瀬戸誠, 依田芳卓, 平尾直久, 河口沙織, 大石泰生, 鈴木慎太郎, 久我健太郎, 中辻知, 小林寿夫, 小林寿夫

    日本物理学会講演概要集(CD-ROM)   72 ( 1 )   2017 （   ISSN:2189-079X ）

  • Physical properties of heavy fermion compound !LaTeX${\alpha}$-YbAlB4 at low temperature under pressure and magnetic fields

    Oura M., Suzuki S., Kuga K., Nakatsuji S., Kobayashi H., Ikeda S., Masuda R., Kobayashi Y., Seto M., Yoda Y., Hirao N., Kawaguchi S. I., Oishi Y.

    Meeting Abstracts of the Physical Society of Japan   72 ( 0 )   2033 - 2033   2017 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.72.1.0_2033

  • 重い電子系化合物α-YbAlB4の低温における圧力・磁場下物性 II

    大浦桃子, 池田修悟, 池田修悟, 増田亮, 小林康浩, 瀬戸誠, 依田芳卓, 平尾直久, 河口沙織, 大石泰生, 鈴木慎太郎, 久我健太郎, 中辻知, 小林寿夫, 小林寿夫

    日本物理学会講演概要集(CD-ROM)   72 ( 2 )   2017 （   ISSN:2189-079X ）

  • Bulk Jeff states of Sr-based iridates studied by cluster-model calculations

    Nakagawa K., Imada S., Saitoh Y., Horiba K., Kumigashira H., Tamasaku K., Yabashi M., Ishikawa T., Takase K., Yamasaki A., Hamamoto S., Kanai Y., Yamagami K., Kuga K., Fujiwara H., Sekiyama A., Higashiya A., Kadono T.

    Meeting Abstracts of the Physical Society of Japan   72 ( 2 )   1211 - 1211   2017 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.72.2.0_1211

  • 重い電子系量子臨界物質YbCo2Ge4におけるYb3d内殻光電子スペクトル線二色性

    久我健太郎, 金井惟奈, 金井惟奈, 藤原秀紀, 藤原秀紀, 藤岡修平, 藤岡修平, 山神光平, 山神光平, 右衛門佐寛, 右衛門佐寛, 青山雄一, 青山雄一, 関山明, 関山明, 東谷篤志, 東谷篤志, 門野利治, 門野利治, 今田真, 今田真, 山崎篤志, 山崎篤志, 玉作賢治, 矢橋牧名, 石川哲也, 北川健太郎, 松林和幸, 木須孝幸, 木須孝幸

    日本放射光学会年会・放射光科学合同シンポジウム(Web)   30th   2017

  • Hard X-ray Photoemission Spectroscopy of 6H-SrIrO3

    Nakagawa K., Kadono T., Imada S., Tamasaku K., Yabashi M., Ishikawa T., Takase K., Yamasaki A., Hamamoto S., Fujioka S., Kanai Y., Yamagami K., Kuga K., Fujiwara H., Sekiyama A., Higashiya A.

    Meeting Abstracts of the Physical Society of Japan   72 ( 1 )   1582 - 1582   2017 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.72.1.0_1582

  • Synchrotron radiation based 174Yb M"ossbauer spectroscopic study of YbAlB4 with external magnetic field

    Kobayashi H., Nakatsuji S., Ohura M., Sakaguchi Y., Ikeda S., Masuda R., Seto M., Yoda Y., Suzuki S., Kuga K.

    Meeting Abstracts of the Physical Society of Japan   71 ( 2 )   1870 - 1870   2016 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    &lt;p&gt;β-YbAlB_4_は零磁場下で極低温において非フェルミ液体性質を示し、80mKで超伝導転移する。一方、α-YbAlB_4_低温でフェルミ液体的であるが、磁場印可によりその低温での性質が大きく変化することが磁化測定などの巨視的測定より明らかとなってきている。我々は、この本質的な物性の違いを、^174^Yb 放射光メスバウアー分法を用いて研究を行っている。今回は、低温（3K）での磁場中^174^Yb 放射光メスバウアー測定を行い、α-YbAlB_4_で観測されている磁場誘起の基底状態変化の微視的原因について議論する。&lt;/p&gt;

    DOI： 10.11316/jpsgaiyo.71.2.0_1870

  • 21pPSA-2 Investigation of electronic structures in the layered oxypnictide LaOMnAs by means of polarization-dependent photoelectron spectroscopy with hard x-ray

    Higashiya A., Abozeed Amina, Kadono T., Imada S., Kuga K., Yabashi M., Tamasaku K., Ishikawa T., Takase K., Nakagawa K., Yamasaki A., Nagai K., Fujioka S., Kanai Y., Yamagami K., Fujiwara H., Sekiyama A.

    Meeting Abstracts of the Physical Society of Japan   71 ( 1 )   1563 - 1563   2016 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.71.1.0_1563

  • Linear dichroism of Yb 3d core level photoelectron spectrum in orthorhombic compound YbCo2Ge4

    Kuga K., Kadono T., Imai S., Yamasaki A., Tamasaku K., Yabashi M., Ishikawa T., Kitagawa K., Matsubayashi K., Kiss T., Kanai Y., Fujiwara H., Fujioka S., Yamagami K., Yomosa H., Aoyama Y., Sekiyama A., Higashiya A.

    Meeting Abstracts of the Physical Society of Japan   71 ( 2 )   2120 - 2120   2016 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.71.2.0_2120

  • 21pBM-1 Surface impedance measurements of β-YbAlB_4 using a tunnel-diode oscillation method under high pressure and high magnetic fields

    Tahara T., Kida T., Kuga K., Nakatsuji S., Kagayama T., Shimizu K., Hagiwara M.

    Meeting Abstracts of the Physical Society of Japan   71 ( 1 )   2298 - 2298   2016 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.71.1.0_2298

  • Unconventional Quantum Criticality in β-YbAlB<inf>4</inf> Detached from Its Magnetically Ordered Phase

    Takahiro Tomita, Kentaro Kuga, Yoshiya Uwatoko, Piers Coleman, Piers Coleman, Satoru Nakatsuji

    Physics Procedia   75   482 - 487   2015.1 （   ISSN:1875-3884 ）

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    © 2015 The Authors. Published by Elsevier B.V. We studied the effect of pressure on the Yb-based heavy-fermion superconductor β-YbAlB 4 (T c =80 mK) near its quantum critical point (QCP) at ambient pressure. Here, the electrical resistivity ρ(T) of the high-quality single crystal (RRR = 300) is measured under hydrostatic pressure P ≃ 2.7 GPa at low temperatures down to 70 mK. The superconducting transition T c gradually decreases with the application of pressure and disappears near 0.9 GPa. However, the non-Fermi liquid (NFL) behavior is found to be robust over a broad range of pressure 0 ≤ P ≤ 0.5 GPa. The NFL state above T c gradually changes to the Fermi liquid state with the application of pressure above P ≃ 0.5 GPa. The magnetic order transition is first observed at 50 mK and P c = 2.7 GPa. The P -T phase diagram indicates that the QCP lying beneath the superconductivity dome is detached from the magnetically ordered phase.

    DOI： 10.1016/j.phpro.2015.12.060

  • 単結晶α-YbAl1-xMnxB4における磁気物性と輸送特性

    鈴木慎太郎, 志村恭通, 久我健太郎, 冨田崇弘, 松本洋介, 中辻知

    日本物理学会講演概要集(CD-ROM)   70 ( 1 )   2015 （   ISSN:2189-079X ）

  • 22pBA-1 X-yay Absorption Spectroscopic Study of β-YbAlB_4 Under Multi Extreme Conditions II

    Sakaguchi Y., Ikeda S., Kawamura N., Mizumaki M., Suzuki S., Kuga K., Nakatsuji S., Ishimatsu N., Kobayashi H.

    Meeting Abstracts of the Physical Society of Japan   70 ( 1 )   2218 - 2218   2015 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.70.1.0_2218

  • 18aDA-6 X-yay Absorption Spectroscopic Study of β-YbAlB_4 Under Multi Extreme Conditions III

    Sakaguchi Y., Ikeda S., Kawamura N., Mizumaki M., Ishimatsu N., Suzuki S., Kuga K., Nakatsuji S., Kobayashi H.

    Meeting Abstracts of the Physical Society of Japan   70 ( 2 )   1981 - 1981   2015 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.70.2.0_1981

  • 強磁場における重い電子系α-YbAl1-xFexB4の磁化とX線磁気円二色性

    寺島拓, 松田康弘, 近藤晃弘, 金道浩一, 鈴木慎太郎, 久我健太郎, 松本洋介, 中辻知, 河村直己, 水牧仁一朗, 稲見俊哉

    日本物理学会講演概要集(CD-ROM)   70 ( 1 )   2015 （   ISSN:2189-079X ）

  • 22pBA-3 Magnetism and transport properties of single crystal α-YbAl_<1-x>Mn_xB_4

    Suzuki S., Shimura Y., Kuga K., Tomita T., Matsumoto Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   70 ( 0 )   2220 - 2220   2015 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.70.1.0_2220

  • 22pBA-2 Magnetization and XMCD of heavy fermion α-YbAl_<1-x>Fe_xB_4 at high magnetic fields

    Terashima T., Mizumaki M., Inami T., Matsuda Y. H., Kondo A., Kindo K., Suzuki S., Kuga K., Matsumoto Y., Nakatsuji S., Kawamura N.

    Meeting Abstracts of the Physical Society of Japan   70 ( 0 )   2219 - 2219   2015 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.70.1.0_2219

  • 22aBJ-2 High-field magnetism of the S=1/2 random triangular lattice antiferromagnet In_2Ga_2CuO_7

    Okutani A., Broholm C., Hagiwara M., Kuga K., Nakano T., Nozue Y., Kimura K., Halim M., Nakatsuji S., Higemoto W., Ito T. U.

    Meeting Abstracts of the Physical Society of Japan   70 ( 1 )   1163 - 1163   2015 （   ISSN:2189-079X   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.70.1.0_1163

  • 28aBE-6 Quantum Critical Phenomena in the Heavy Fermion Valence Fluctuating System α-YbAl_<1-x>Fe_xB_4

    Kuga K., Matsumoto Y., Suzuki S., Nakatsuji S.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   583 - 583   2014.3 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.1.3.0_583_4

  • 価数揺動物質α-YbAl1-xFexB4(x=0.014)における電子臨界現象

    久我健太郎, 久我健太郎, 松本洋介, 鈴木慎太郎, 中辻知

    日本物理学会講演概要集   69 ( 1 )   2014 （   ISSN:1342-8349 ）

  • 8aPS-83 X-yay Absorption Spectroscopic Study of β-YbAlB_4 Under Multi Extreme Conditions

    Sakaguchi Y., Ikeda S., Kawamura N., Mizumaki M., Suzuki S., Kuga K., Nakatsuji S., Ishimatsu N., Kobayashi H.

    Meeting Abstracts of the Physical Society of Japan   69 ( 2 )   376 - 376   2014 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.2.3.0_376_4

  • 価数揺動系α-YbAl1-xMnxB4の磁性と伝導

    鈴木慎太郎, 曾根啓太, 久我健太郎, 志村恭通, 松本洋介, 中辻知

    日本物理学会講演概要集   69 ( 1 )   2014 （   ISSN:1342-8349 ）

  • 価数揺動系α-YbAl1-xMnxB4における輸送特性の組成依存性

    鈴木慎太郎, 志村恭通, 久我健太郎, 冨田崇弘, 松本洋介, 中辻知

    日本物理学会講演概要集   69 ( 2 )   2014 （   ISSN:1342-8349 ）

  • 価数揺動系α-YbAl1-xFexB4の極低温比熱測定

    松本洋介, 久我健太郎, 中辻知

    日本物理学会講演概要集   69 ( 2 )   2014 （   ISSN:1342-8349 ）

  • 28aBE-3 Pressure-induced Electronic State Change of Yb ions at Low Temperature in Valence Fluctuating β-YbAlB_4

    Sakaguchi Y., Ishimatsu N., Kobayashi H., Ikeda S., Kawamura N., Mizumaki M., Hirao N., Ohishi Y., Suzuki S., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   69 ( 1 )   583 - 583   2014 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.1.3.0_583_1

  • 28aBE-5 Fe-doping Effect and the Quantum Criticality of Heavy Fermion System β-YbAlB_4

    Tomita T., Kuga K., Matsumoto Y., Nakatsuji S., Matsubayashi K., Uwatoko Y.

    Meeting Abstracts of the Physical Society of Japan   69 ( 1 )   583 - 583   2014 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.1.3.0_583_3

  • 重い電子系α-YbAl1-xFexB4の強磁場磁化過程と価数 II

    寺島拓, 松田康弘, 近藤晃弘, 金道浩一, 久我健太郎, 松本洋介, 中辻知, 河村直己, 水牧仁一朗, 稲見俊哉

    日本物理学会講演概要集   69 ( 1 )   2014 （   ISSN:1342-8349 ）

  • 10aBD-2 Magnetization of heavy fermion α-YbAlB_4 at high magnetic fields

    Terashima T., Matsuda Y. H., Kondo A., Kindo K., Suzuki S., Kuga K., Matsumoto Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   69 ( 2 )   448 - 448   2014 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    Language：Japanese   Publisher：The Physical Society of Japan  

    DOI： 10.11316/jpsgaiyo.69.2.3.0_448_2

  • 28aCM-6 Low Temperature Thermodynamics Properties of Ba_3CuSb_2O_9

    HALIM Mario

    Meeting Abstracts of the Physical Society of Japan   69   591 - 591   2014 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.1.3.0_591_4

  • 28aBE-2 NMR studies on heavy fermion compounds β-LnAlB_4 (Ln=Yb, Lu) II

    Takano Shun, Grbic M.S., Yoshida M., Takigawa M., Suzuki S., O'Farrell E.C.T., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   69 ( 1 )   582 - 582   2014 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.1.3.0_582_4

  • 10aBD-3 NMR studies on heavy fermion compounds β-LnAlB_4 (Ln=Yb, Lu) III

    Takano Shun, Grbic M. S., Yoshida M., Takigawa M., Suzuki S., O'Farrell E. C. T., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   69 ( 2 )   448 - 448   2014 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.2.3.0_448_3

  • 10aBD-1 Low Temperature Specific Heat Studies of Valence Fluctuating α-YbAl_<1-x>Fe_xB_4

    Matsumoto Y., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   69 ( 0 )   448 - 448   2014 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.2.3.0_448_1

  • 10aBD-4 Composition dependence of transport properties in the intermediate valence system α-YbAl_<1-x>Mn_xB_4

    Suzuki S., Shimura Y, Kuga K., Tomita T., Matsumoto Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   69 ( 0 )   448 - 448   2014

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    Language：Japanese   Publisher：The Physical Society of Japan  

    DOI： 10.11316/jpsgaiyo.69.2.3.0_448_4

  • 28aBE-4 Magnetism and transport in the intermediate valence system α-YbAl_<1-x>Mn_xB_4

    Suzuki S., Sone K., Kuga K., Shimura Y., Matsumoto Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   69 ( 0 )   583 - 583   2014 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.1.3.0_583_2

  • 28aBE-7 Magnetization and valence state in Yb-based heavy fermion compounds α-YbAl_<1-x>Fe_xB_4 at high magnetic fields II

    Terashima T., Inami T., Matsuda Y. H., Kondo A., Kindo K., Kuga K., Matsumoto Y., Nakatsuji S., Kawamura N., Mizumaki M.

    Meeting Abstracts of the Physical Society of Japan   69 ( 0 )   584 - 584   2014 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.1.3.0_584_1

  • 27aPS-72 Spin glass transition in single crystal of Mn alloys

    Iritani K., Higo T., Kuga K., Nugroho A. A., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   69 ( 1 )   491 - 491   2014 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.69.1.3.0_491_3

  • Single crystal study of low temperature magnetism of the intermediate valence system α-Yb(Al,Mn)B_4

    Suzuki S., Sone K., Kuga K., Shimura Y., Matsumoto Y., Nakatsuji S.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   541 - 541   2013.8 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

    DOI： 10.11316/jpsgaiyo.68.2.3.0_541_4

  • 26aKQ-2 Synthesis and Characterization of Ba_3CuSb_2O_9 Single Crystal

    HALIM Mario

    Meeting Abstracts of the Physical Society of Japan   68 ( 2 )   499 - 499   2013.8 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.2.3.0_499_2

  • 26pEB-2 NMR study of heavy-fermion system α-YbAlB_4

    GRBIC M.S., KIMURA K., YOSHIDA M., TAKIGAWA M., KUGA K., NAKATSUJI S.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   540 - 540   2013.8 （   ISSN:1342-8349 ）

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  • Conduction electron spin resonance in AlB<inf>2</inf>

    L. M. Holanda, L. Mendonça-Ferreira, R. A. Ribeiro, J. M. Osorio-Guillén, G. M. Dalpian, K. Kuga, S. Nakatsuji, Z. Fisk, R. R. Urbano, P. G. Pagliuso, C. Rettori

    Journal of Physics Condensed Matter   25 ( 21 )   2013.5 （   ISSN:0953-8984   eISSN:1361-648X ）

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    This work reports on electron spin resonance experiments in oriented single crystals of the hexagonal AlB2 diboride compound (P6/mmm, D16h structure) which display conduction electron spin resonance. The X-band electron spin resonance spectra showed a metallic Dysonian resonance with g-value and intensity independent of temperature. The thermal broadening of the anisotropic electron spin resonance linewidth ΔH tracks the T-dependence of the electrical resistivity below T ≃ 100 K. These results confirm the observation of a conduction electron spin resonance in AlB2 and are discussed in comparison with other boride compounds. Based on our main findings for AlB2 and the calculated electronic structure of similar layered honeycomb-like structures, we conclude that any array of covalent B-B layers potentially results in a conduction electron spin resonance signal. This observation may shed new light on the nature of the non-trivial conduction electron spin resonance-like signals of complex f-electron systems such as β-YbAlB4. © 2013 IOP Publishing Ltd.

    DOI： 10.1088/0953-8984/25/21/216001

  • 29pXY-5 ESR in single crystals of Ba_3CuSb_2O_9 (orthorhombic)

    Hagiwara M., Han Y., Kuga K., Kimura K., Nakatsuji S., Nakano T., Nozue Y.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   726 - 726   2013.3 （   ISSN:1342-8349 ）

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  • 28pXA-8 Hall effect measurements of the quantum critical and valence fluctuating β-YbAlB_4 under pressure

    O'Farrell E. C. T., Kuga K., Matsumoto Y., Matsubayashi K., Tomita T., Uwatoko Y., Nakatsuji S.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   670 - 670   2013.3 （   ISSN:1342-8349 ）

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  • 29pXY-4 ESR in single crystals of Ba_3CuSb_2O_9 (hexagonal)

    Han Y., Hagiwara M., Kuga K., Kimura K., Nakatsuji S., Nakano T., Nozue Y.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   726 - 726   2013.3 （   ISSN:1342-8349 ）

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  • 価数揺動物質YbAlB4の174Yb放射光メスバウアー分光法による研究

    阪口友唯, 池田修悟, 増田亮, 小林康浩, 瀬戸誠, 依田芳卓, 久我健太郎, 中辻知, 小林寿夫

    日本物理学会講演概要集   68 ( 1 )   2013 （   ISSN:1342-8349 ）

  • 価数揺動系α-YbAl1-xTxB4(T:遷移金属)における磁性と熱膨張

    曾根啓太, 久我健太郎, 木村健太, 松本洋介, 中辻知

    日本物理学会講演概要集   68 ( 1 )   2013 （   ISSN:1342-8349 ）

  • Fe-Doping and Temperature Dependence of Yb Valence in the Mixed Valence System α-Yb(Al,Fe)B_4

    Okawa M., Shin S., Kuga K., Nakatsuji S., Saitoh T., Kasahara A., Taji T., Yamamura S., Wadati H., Yoshida T., Sugimyama T., Ikenaga E., Taguchi M.

    Meeting Abstracts of the Physical Society of Japan   68 ( 2 )   541 - 541   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.2.3.0_541_3

  • 価数揺動系YbAl1-xMnxB4の単結晶における低温磁性

    鈴木慎太郎, 曾根啓太, 久我健太郎, 志村恭通, 松本洋介, 中辻知

    日本物理学会講演概要集   68 ( 2 )   2013 （   ISSN:1342-8349 ）

  • 28pXA-10 Pressure-induced Valence Change of Yb ions in Valence Fluctuating β-YbAlB_4

    Sakaguchi Y., Kobayashi H., Ikeda S., Kuga K., Sone K., Nakatsuji S., Hirao N., Ohishi Y., Kawamura N., Mizumaki J.

    Meeting Abstracts of the Physical Society of Japan   68 ( 1 )   670 - 670   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.1.3.0_670_4

  • Pressure induced Valence Change of Yb ions at Low Temperature in Valence Fluctuating βYbAlB_4.

    Sakaguchi Y., Ikeda S., Kawamura N., Mizumaki M., Kuga K., Nakatsuji S., Kobayashi H.

    Meeting Abstracts of the Physical Society of Japan   68 ( 2 )   465 - 465   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.2.3.0_465_2

  • 29pXY-8 Magnetic order and frustration in spinel sulfides AYb_2S_4(A=Cd,Mg)

    Iritani K., Halim Mario, Sakai A., Kuga K., Kimura K., Karaki Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 1 )   727 - 727   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.1.3.0_727_3

  • Anisotropic Magnetic Field Evolution of Nuclear Spin-Lattice Relaxation in α-YbAlB_4 Studied by Low Tempereture Themal Relaxation

    Matsumoto Y., Hong J., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 2 )   540 - 540   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.2.3.0_540_4

  • 29pXY-1 Single crystal growth and physical properties of the orbitally-active honeycomb-based quantum magnet Ba_3CuSb_2O_9

    Kimura K., Halim Mario, Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 1 )   725 - 725   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.1.3.0_725_4

  • 重い電子系α-YbAl1-xFexB4の強磁場磁化過程

    寺島拓, 松田康弘, 近藤晃弘, 金道浩一, 久我健太郎, 松本洋介, 中辻知

    日本物理学会講演概要集   68 ( 2 )   2013 （   ISSN:1342-8349 ）

  • Two Types of Magnetic Ordered Phases induced by Fe doping in the Heavy Fermion Valence Fluctuating System α-YbAlB_4

    Kuga K., Sone K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 2 )   541 - 541   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.2.3.0_541_1

  • 28pXA-14 Magnetic Field Evolution of the Heavy Fermion State in YbAlB_4 Studied by Low Temperature Specific Heat Measurements

    Matsumoto Y, Hong J., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 1 )   671 - 671   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.1.3.0_671_4

  • 28pXA-15 Transport study on the metamagnetism in α-YbAlB_4

    Hong J., Matsumoto Y., O'Farrell E. C. T., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 1 )   672 - 672   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.1.3.0_672_1

  • NMR studies on heavy fermion compounds β-LnAlB_4(Ln=Yb,Lu)

    Takano Shun, Grbic M.S., Yoshida M., Takigawa M., Suzuki S., O'Farrell E.C.T., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 2 )   539 - 539   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.2.3.0_539_4

  • 28pXA-12 NMR study on heavy fermion single crystal β-YbAlB_4

    Takano Shun, Grbic M., Yoshida M., Takigawa M., O'Farrell E. C. T., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 1 )   671 - 671   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.1.3.0_671_2

  • Magnetization process of Yb-based heavy fermion compounds α-YbAl_<1-x>Fe_xB_4 in high magnetic fields

    Terashima T., Matsuda Y.H., Kondo A., Kindo K., Kuga K., Matsumoto Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 0 )   541 - 541   2013 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.2.3.0_541_2

  • 27aPS-42 Magnetism and thermal expansion in the valence fluctuating compound a-YbAl_<1-x>T_xB_4 (T: Transition metal)

    Sone K., Kuga K., Kimura K., Matsumoto Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 0 )   619 - 619   2013 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.1.3.0_619_3

  • 28pXA-11 ^<174>Yb Mossbauer Spectroscopic Study of YbAlB_4 using synchrotron radiation

    Sakaguchi Y., Ikeda S., Masuda R., Kobayashi Y., Seto M., Yoda Y., Kuga K., Nakatsuji S., Kobayashi H.

    Meeting Abstracts of the Physical Society of Japan   68 ( 0 )   671 - 671   2013 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.1.3.0_671_1

  • 28pXA-9 Quantum Critical Phenomena and Pressure phase diagram in β-YbAlB_4

    Tomita T., Ebata M., Takaahshi T., Kuga K., Matsumoto Y., Nakatsuji S., Matsubayashi K., Uwatoko Y.

    Meeting Abstracts of the Physical Society of Japan   68 ( 0 )   670 - 670   2013 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.1.3.0_670_3

  • Ba3CuSb2O9の強磁場多周波ESR

    萩原政幸, HAN Y., 木村健太, 久我健太郎, 中辻知, 中野岳仁, 野末泰夫

    日本物理学会講演概要集   68 ( 2 )   2013 （   ISSN:1342-8349 ）

  • Magnetic Field Response of Heavy Fermion System β-YbAlB_4 at Low Temperature and under High Pressure.

    Tomita T., Shimura Y., Kuga K., Matsumoto Y., Takahashi T., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   68 ( 2 )   540 - 540   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.2.3.0_540_2

  • Partially disordered state of triangular lattice antiferromagnet NaCo(Acac)_3 benzene

    Karaki Y., Kuga K., Kimura K., Matsubayashi K., Uwatoko Y.

    Meeting Abstracts of the Physical Society of Japan   68 ( 2 )   361 - 361   2013 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.68.2.3.0_361_2

  • β-YbAl1-xFexB4における量子臨界現象と圧力相図

    冨田崇弘, 江畑政哉, 高橋博樹, 久我健太郎, 松本洋介, 中辻知, 松林和幸, 上床美也

    日本物理学会講演概要集   68 ( 1 )   2013 （   ISSN:1342-8349 ）

  • Magnetic order induced by Fe substitution of Al site in the heavy-fermion systems α-YbAlB4 and β-YbAlB4

    Kentaro Kuga, Gregory Morrison, Larico Treadwell, Julia Y. Chan, Satoru Nakatsuji

    Physical Review B - Condensed Matter and Materials Physics   86   2012.12 （   ISSN:1098-0121 ）

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    β-YbAlB 4 is a heavy-fermion superconductor that exhibits a quantum criticality without tuning at zero field and under ambient pressure. We have succeeded in substituting Fe for Al in β-YbAlB 4 as well as the polymorphous compound α-YbAlB 4 , which in contrast has a heavy Fermi-liquid ground state. Full structure determination by single-crystal x-ray diffraction confirmed no change in crystal structure for both α- and β-YbAlB 4 , in addition to volume contraction with Fe substitution. Our measurements of the magnetization and specific heat indicate that both α-YbAl 0.93 Fe 0.07 B 4 and β-YbAl 0.94 Fe 0.06 B 4 exhibit a magnetic order, most likely of a canted antiferromagnetic type, at 7∼9 K. The increase in the entropy as well as the decrease in the antiferromagnetic Weiss temperature with the Fe substitution in both systems indicates that the chemical pressure due to the Fe substitution suppresses the Kondo temperature and induces the magnetism. © 2012 American Physical Society.

    DOI： 10.1103/PhysRevB.86.224413

  • 21aFH-11 Hall effect measurements around the quantum critical point in the valence fluctuating YbAlB_4 system

    O'Farrell E.C.T., Kuga K., Matsumoto Y., Matsubayashi K., Uwatoko Y., Nakatsuji S.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   580 - 580   2012.8 （   ISSN:1342-8349 ）

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  • 24aYB-3 Hall effect measurements of the valence fluctuating heavy fermion β-YbAlB_4 under pressure

    O'Farrell E. C. T., Kuga K., Matsumoto Y., Tomita T., Matsubayashi K., Uwatoko Y., Nakatsuji S.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   545 - 545   2012.3 （   ISSN:1342-8349 ）

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  • 価数揺動物質Yb(Al1-xFex)B4の圧力下物性

    阪口友唯, 池田修悟, 久我健太郎, 曾根啓太, 中辻知, 平尾直久, 大石泰生, 小林寿夫

    日本物理学会講演概要集   67 ( 2 )   2012 （   ISSN:1342-8349 ）

  • 四極子近藤格子系PrTr2Al20(Tr=Ti,V)における極低温物性

    酒井明人, 久我健太郎, FARRELL E. C. T. O’, 松本洋介, 柄木良友, 中辻知

    日本物理学会講演概要集   67 ( 2 )   2012 （   ISSN:1342-8349 ）

  • 21aFH-10 Thermal expansion and impurity substitution effect in the valence fluctuation system YbAlB_4

    Sone K., Kuga K., Matsumoto Y., Nakatsuji S., Terashima T., Matsuda Y., Nagasawa T., Matsuda K.

    Meeting Abstracts of the Physical Society of Japan   67 ( 2 )   580 - 580   2012 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.2.3.0_580_1

  • 24pPSB-71 Mossbauer spectroscopy of Fe doping Valence fluctuating α-YbAlB_4

    Sakaguchi Y., Ikeda S., Kuga K., Sone K., Nakatsuji S., Kobayashi H.

    Meeting Abstracts of the Physical Society of Japan   67 ( 1 )   581 - 581   2012 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.1.3.0_581_1

  • 価数揺動物質Yb(Al1-xFex)B4の高圧力下構造解析

    阪口友唯, 池田修悟, 小林寿夫, 久我健太郎, 曾根啓太, 中辻知, 平尾直久, 大石泰生

    高圧討論会講演要旨集   53rd   2012 （   ISSN:0917-6373 ）

  • 24aYB-1 High-pressure NMR study of α-YbAlB_4

    Kimura K., Yamauchi I., Takigawa M., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   67 ( 1 )   544 - 544   2012 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.1.3.0_544_4

  • YbAl1-xFexB4の単結晶育成と熱膨張

    曾根啓太, 久我健太郎, 松本洋介, 中辻知, 長澤亨

    日本物理学会講演概要集   67 ( 1 )   2012 （   ISSN:1342-8349 ）

  • 重い電子系Yb化合物β-YbAlB4の圧力誘起量子臨界現象

    冨田崇弘, 高橋博樹, 江畑政哉, 久我健太郎, 中辻知, 松林和幸, 上床美也

    高圧討論会講演要旨集   53rd   2012 （   ISSN:0917-6373 ）

  • 重い電子系α-YbAl1-xFexB4の強磁場磁化と価数

    寺島拓, 松田康弘, 中辻知, 久我健太郎, 曾根啓太, 河村直己, 水牧仁一朗, 稲見俊哉

    日本物理学会講演概要集   67 ( 2 )   2012 （   ISSN:1342-8349 ）

  • 24aYB-2 NMR study of α-YbA1B4

    Tajima K., Takigawa M., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   67 ( 1 )   545 - 545   2012 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.1.3.0_545_1

  • 24aYB-4 Low temperature specific heat study of the metamagnetism in α-YbAlB_4

    Hong J., Matsumoto Y., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   67 ( 1 )   545 - 545   2012 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.1.3.0_545_3

  • 19pHC-1 Ultralow temperature properties of the quadrupolar Rondo lattice system PrTr_2Al_<20> (Tr=Ti, V)

    Sakai A., Kuga K., O'Farrell E. C. T., Matsumoto Y., Karaki Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   67 ( 0 )   490 - 490   2012 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.2.3.0_490_4

  • 20aPSA-72 Cu, Ga-NMR Study of Pr (Cu, Ga)_<13>

    Tokunaga Y., Sakai H., Kambe S., Shimura Y., Kuga K., Sakakibara S., Cho J. Y., Chan J. Y.

    Meeting Abstracts of the Physical Society of Japan   67 ( 0 )   523 - 523   2012 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.2.3.0_523_3

  • 20aPSB-16 Magnetization and valence state in a heavy fermion compound YbAl_<1-x>Fe_xB_4 at high magnetic fields

    Terashima T., Matsuda Y. H., Nakatsuji S., Kuga K., Sone K., Kawamura N., Mizumaki M., Inami T.

    Meeting Abstracts of the Physical Society of Japan   67 ( 0 )   527 - 527   2012 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.2.3.0_527_4

  • 20aPSB-17 Structural Properties of Valence Fluctuating Yb(Al_<1-x>Fe_x)B_4 Under Hydrostatic Pressure

    Sakaguchi Y., Ikeda S., Kuga K., Sone K., Nakatsuji S., Hirao N., Ohishi Y., Kobayashi H.

    Meeting Abstracts of the Physical Society of Japan   67 ( 0 )   528 - 528   2012 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.2.3.0_528_1

  • 24aYB-5 Single crystal growth and thermal expansion of YbAl_<1-x>Fe_xB_4

    Sone K., Kuga K., Matsumoto Y., Nakatsuji S., Nagasawa T.

    Meeting Abstracts of the Physical Society of Japan   67 ( 0 )   545 - 545   2012 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.1.3.0_545_4

  • 24aYB-6 Quantum Critical Phenomena Induced by Fe doping in the Valence Fluctuating System α-YbAlB_4

    Kuga K., Sone K., Matsumoto Y., O'Farrell E. C. T., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   67 ( 0 )   546 - 546   2012 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.67.1.3.0_546_1

  • 価揺動物質α-YbAl1-xFexB4の磁場中低温物性

    久我健太郎, 曾根啓太, 松本洋介, O’FARRELL E. C. T., 中辻知

    日本物理学会講演概要集   67 ( 1 )   2012 （   ISSN:1342-8349 ）

  • Pr(Cu,Ga)13のCu,Ga-NMRによる研究

    徳永陽, 酒井宏典, 神戸振作, 志村恭通, 久我健太郎, 榊原俊郎, CHO J. Y., CHAN J. Y.

    日本物理学会講演概要集   67 ( 2 )   2012 （   ISSN:1342-8349 ）

  • 22aGC-10 Hall effect measurements of the valence fluctuating heavy fermion β-YbAlB_4

    O'Farrell E., Matsumoto Y., Kuga K., Nakatsuji S.

    Meeting abstracts of the Physical Society of Japan   66 ( 2 )   494 - 494   2011.8 （   ISSN:1342-8349 ）

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  • NMR/NQR and specific heat studies of iron pnictide superconductor KFe <inf>2</inf>As<inf>2</inf>

    H. Fukazawa, T. Saito, Y. Yamada, K. Kondo, M. Hirano, Y. Kohori, K. Kuga, A. Sakai, Y. Matsumoto, S. Nakatsuji, K. Kihou, A. Iyo, C. H. Lee, H. Eisaki

    Journal of the Physical Society of Japan   80 ( SUPPL. A )   2011.7 （   ISSN:0031-9015   eISSN:1347-4073 ）

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    We report the 75As nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR) and specific heat measurements of the heavily hole-doped superconductor KFe2As2 (superconducting transition temperature Tc ≃ 3.5 K) using high quality single crystals. NMR Knight shifts in superconducting state clearly indicate that spin-singlet superconductivity realizes in this material. It is noted that the electronic specific heat coefficient of the material is 93.0 mJ/K 2mol-fu and that the value is quite heavy for d electron system. © 2011 The Physical Society of Japan.

    DOI： 10.1143/JPSJS.80SA.SA118

  • 26aEC-2 Quantum oscillations and the Fermi surface of the heavy fermion α-YbAlB_4 across a meta-magnetic transition

    O'Farrell E.C.T., Tompsett D.A., Horie N., Kuga K., Yamaura J., Nakatsuji S., Sutherland M.L.

    Meeting abstracts of the Physical Society of Japan   66 ( 1 )   582 - 582   2011.3 （   ISSN:1342-8349 ）

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  • 22aGC-8 Magneto-resistance of the valence fluctuating system YbAlB_4 and possibility of its anisotropic heavy electron formation

    Hong J. P., Matsumoto Y., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   66 ( 2 )   494 - 494   2011 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.2.3.0_494_1

  • 22aGC-12 Anisotropic heavy Fermi-liquid formation in the valence fluctuating α-YbAlB_4

    Matsumoto Y., Kuga K., Tomita T., Karaki Y., O'Farrell Eoin, Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   66 ( 2 )   495 - 495   2011 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.2.3.0_495_1

  • 26aEC-4 Magnetism and Valence Change Induced by Fe doping in the Valence Fluctuating Heavy Fermion System α-YbAlB_4

    Kuga K., Shin S., Nishino Y., Tamasaku K., Yabashi M., Ishikawa T., Kiuchi Y., Matsumoto Y., Nakatsuji S., Okawa M., Takata Y., Matsunami M., Eguchi R., Taguchi M., Chainani Ashish

    Meeting Abstracts of the Physical Society of Japan   66 ( 1 )   582 - 582   2011 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.1.3.0_582_3

  • α-YbAlB4のNMR

    田島一樹, 瀧川仁, 久我健太郎, 中辻知

    日本物理学会講演概要集   66 ( 2 )   2011 （   ISSN:1342-8349 ）

  • 重い電子系β-YbAl1-xFexB4の圧力誘起相転移

    白崎暢大, 冨田崇弘, 冨田崇弘, 高橋博樹, 高橋博樹, 久我健太郎, 中辻知, 松林和幸, 上床美也

    日本物理学会講演概要集   66 ( 2 )   2011 （   ISSN:1342-8349 ）

  • 26aEC-1 T/B scaling and its Free Energy in the Heavy Fermion Systems β-YbAlB_4

    Matsumoto Y., Nakatsuji S., Kuga K., Karaki Y., Shimura Y., Sakakibara T., Nevidomskyy A.H., Coleman P.

    Meeting Abstracts of the Physical Society of Japan   66 ( 1 )   581 - 581   2011 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.1.3.0_581_4

  • 22aGC-13 Quantum Critical Phenomena Induced by Fe doping in the Valence Fluctuating Heavy Fermion System α-YbAlB_4

    Kuga K., Chainani Ashish, Shin S., Nishino Y., Tamasaku K., Yabashi M., Ishikawa T., Kiuchi Y., O'Farrell E. C. T., Matsumoto Y., Nakatsuji S., Okawa M., Takata Y., Matsunami M., Eguchi R., Taguchi M.

    Meeting Abstracts of the Physical Society of Japan   66 ( 2 )   495 - 495   2011 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.2.3.0_495_2

  • 22aGC-9 Thermal expansion of heavy fermion valence fluctuation materials YbAlB_4

    Sone K., Kuga K., Matsumoto Y., Kimura K., Matsuda K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   66 ( 2 )   494 - 494   2011 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.2.3.0_494_2

  • α-YbAlB4のNMR

    田島一樹, 瀧川仁, 久我健太郎, 中辻知

    日本物理学会講演概要集   66 ( 1 )   2011 （   ISSN:1342-8349 ）

  • 22aGC-11 NMR study of α-YbAlB_4

    Tajima K., Takigawa M., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   66 ( 0 )   494 - 494   2011 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.2.3.0_494_4

  • 23aGB-11 ESR in Ba_3CuSb_2O_9

    Hagiwara M., Ishii R., Kuga K., Kimura K., Nakatsuji S., Nakano T., Nozue Y.

    Meeting Abstracts of the Physical Society of Japan   66 ( 0 )   569 - 569   2011 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.2.3.0_569_1

  • 23aGB-12 Low Temperature Magnetism of Ba_3CuSb_2O_9

    Nakatsuji S., Kuga K., Kimura K., Ishii R., Rodriguez J. A., Broholm C.

    Meeting Abstracts of the Physical Society of Japan   66.2.3   569   2011 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.2.3.0_569_2

  • 23aPS-48 Pressure-induced phase transition of the heavy fermion system β-YbAl_<1-x>Fe_xB_4

    Shirasaki N., Tomita T., Takahashi H., Kuga K, Nakatsuji S., Matsubayashi K., Uwatoko Y.

    Meeting Abstracts of the Physical Society of Japan   66 ( 0 )   588 - 588   2011 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.2.3.0_588_2

  • 26aEC-3 NMR of α-YbAlB_4

    Tajima K., Takigawa M., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   66 ( 0 )   582 - 582   2011 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.66.1.3.0_582_2

  • Ba3CuSb2O9のESR

    萩原政幸, 石井梨恵子, 久我健太郎, 木村健太, 中辻知, 中野岳仁, 野末泰夫

    日本物理学会講演概要集   66 ( 2 )   2011 （   ISSN:1342-8349 ）

  • Ba3CuSb2O9の低温磁性

    中辻知, 久我健太郎, 木村健太, 石井梨恵子, RODRIGUEZ J. A., BROHOLM C., BROHOLM C.

    日本物理学会講演概要集   66 ( 2 )   2011 （   ISSN:1342-8349 ）

  • Low-temperature thermal transport coefficients of heavy fermion β-YbAlB<inf>4</inf>

    Y. MacHida, C. Ogura, K. Izawa, K. Kuga, S. Nakatsuji

    Journal of Physics: Conference Series   273 ( 1 )   2011 （   ISSN:1742-6588   eISSN:1742-6596 ）

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    The first Yb-based heavy fermion superconductor β-YbAlB4 with Tc = 80 mK is stoichiometrically quantum critical under ambient pressure and under zero magnetic field. We report the low-temperature thermoelectric power S(T) on a high-quality single crystal of β-YbAlB 4 down to 40 mK. In zero field, S(T)/T exhibits a dramatic enhancement and takes large negative values at low temperatures, followed by a fast drop below 80 mK as an indication of the superconducting transition. Under the field of B = 25 mT (≥ Bc2), -S(T)/T is found to continuously increase down to the lowest temperature, which is highly in contrast to what is expected for the Fermi liquids (S/T ∼ const.). © Published under licence by IOP Publishing Ltd.

    DOI： 10.1088/1742-6596/273/1/012005

  • 21aGD-3 Quantum Phase Transition Induced by Chemical Substitution in the Valence Fluctuating Systems YbAlB_4

    Kuga K., Karaki Y., Matsumoto Y., Tomita T., Horie N., Yamaura J., Kiuchi Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   65 ( 1 )   591 - 591   2010 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.65.1.3.0_591_3

  • 23aWG-3 Quantum criticality of heavy fermion β-YbAlB_4 probed by thermal conductivity

    Machida Y., Ogura C., Izawa K., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   65 ( 2 )   449 - 449   2010 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.65.2.3.0_449_1

  • 21aGD-4 Lu dilution effects in the Heavy Fermion Systems α-, β-YbAlB_4

    Matsumoto Y., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   65 ( 1 )   591 - 591   2010 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.65.1.3.0_591_4

  • 23aWG-1 Magnetic and Transport Properties of Lu dilution Systems of the Heavy Fermion Systems α-, β-YbAlB_4

    Matsumoto Y., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   65 ( 2 )   448 - 448   2010 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.65.2.3.0_448_3

  • 21aGD-2 Quantum Criticality in the Heavy Fermion System β-YbAlB_4 at Low Temperature under Pressure

    Tomita T., Kuga K., Horie N., Matsumoto Y., Nakatsuji S., Ueda H., Matsubayashi K., Matsumoto T., Uwatoko Y.

    Meeting Abstracts of the Physical Society of Japan   65 ( 1 )   591 - 591   2010 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.65.1.3.0_591_2

  • 21aGD-1 Low temperature thermal transport coefficients of heavy fermion β-YbAlB_4

    Machida Y., Ogura C., Izawa K., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   65 ( 1 )   591 - 591   2010 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.65.1.3.0_591_1

  • α-YbAlB4のNMR

    田島一樹, 瀧川仁, 久我健太郎, 中辻知

    日本物理学会講演概要集   65 ( 2 )   2010 （   ISSN:1342-8349 ）

  • 23aPS-61 Low Temperature Specific Heat Measurements of the FeAs-based Superconductor

    Deguchi K., Kihou K., Lee C-H., Iyo A., Eisaki H., Osaki E., Sato N. K., Saito T., Fukazawa H., Kohori Y., Kuga K., Matsumoto Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   65 ( 2 )   474 - 474   2010 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.65.2.3.0_474_1

  • 23aWG-2 NMR of α-YbAlB_4

    Tajima K., Takigawa m., Kuga K., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   65 ( 0 )   448 - 448   2010 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.65.2.3.0_448_4

  • Crystal growth, structure, and physical properties of Ln(Cu,Al)<inf>12</inf>(Ln = y , Ce, Pr, Sm, and Yb) and Ln(Cu,Ga)<inf>12</inf> (Ln = Y, Gd-Er, and Yb)

    Brenton L. Drake, C. Capan, Jung Young Cho, Y. Nambu, K. Kuga, Y. M. Xiong, A. B. Karki, S. Nakatsuji, P. W. Adams, D. P. Young, Julia Y. Chan

    Journal of Physics Condensed Matter   22 ( 6 )   2010 （   ISSN:0953-8984   eISSN:1361-648X ）

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    Single crystals of Ln(Cu,Al)12 and Ln(Cu,Ga)12 compounds (Ln = Y, Ce-Nd, Sm, Gd-Ho, and Yb for Al and Ln = Y, Gd-Er, Yb for Ga) have been grown by flux-growth methods and characterized by means of single-crystal x-ray diffraction, complemented with microprobe analysis, magnetic susceptibility, resistivity and heat capacity measurements. Ln(Cu,Ga)12 and Ln(Cu,Al)12 of the ThMn12 structure type crystallize in the tetragonal I4/mmm space group with lattice parameters a∼8.59 and c∼5.15 and a∼8.75and c∼5.13 for Ga and Al containing compounds, respectively. For aluminium containing compounds, magnetic susceptibility data show Curie-Weiss paramagnetism in the Ce and Pr analogues down to 50K with no magnetic ordering down to 3K, whereas the Yb analogue shows a temperature-independent Pauli paramagnetism. Sm(Cu,Al)12 orders antiferromagnetically at TN∼5K and interestingly exhibits Curie-Weiss behaviour down to 10K with no Van Vleck contribution to the susceptibility. Specific heat data show that Ce(Cu,Al)12 is a heavy fermion antiferromagnet with TN∼2K and with an electronic specific heat coefficient γ0 as large as 390mJK2mol-1. In addition, this is the first report of Pr(Cu,Al)12 and Sm(Cu,Al)12 showing an enhanced mass (∼80 and 120mJK2mol-1). For Ga containing analogues, magnetic susceptibility data also show the expected Curie-Weiss behaviour from Gd to Er, with the Yb analogue being once again a Pauli paramagnet. The antiferromagnetic transition temperatures range over 12.5, 13.5, 6.7, and 3.4K for Gd, Tb, Dy, and Er. Metallic behaviour is observed down to 3K for all Ga and Al analogues. A large positive magnetoresistance up to 150% at 9T is also observed for Dy(Cu,Ga)12. The structure, magnetic, and transport properties of these compounds will be discussed. © 2010 IOP Publishing Ltd.

    DOI： 10.1088/0953-8984/22/6/066001

  • Crystal growth, structure, and physical properties of Ln(Cu,Ga) <inf>3-x</inf>(Ln=La-Nd, Eu; x≈0.2)

    Jung Young Cho, Evan L. Thomas, Yusuke Nambu, Cigdem Capan, Amar B. Karki, David P. Young, Kentarou Kuga, Satoru Nakatsuji, Julia Y. Chan

    Chemistry of Materials   21 ( 14 )   3072 - 3078   2009.7 （   ISSN:0897-4756 ）

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    Single crystals of Ln(Cu,Ga) 13-x(Ln=La-Nd, Eu; x≈0.2) were grown using Ga flux and their structures determined by single-crystal X-ray diffraction. The Ln(Cu,Ga) 13-x (Ln=La-Nd, Eu; x≈0.2), adopting NaZn 13 structure type, crystallizes in the cubic Fm3̄c (No. 226) space group, with Z=8 and lattice parameters a≈11.8A° .Magnetic susceptibility and heat capacity measurements do not show any indication of long-range magnetic ordering down to 2 K for magnetic analogues. Metallic behavior is observed in the range of 2-300 K for each compound. A large positive magnetoresistance up to 154% at a field (μ )OH) of 9 T is also observed for Pr(Cu,Ga) 12.85(1). Most interestingly, the Pr analogue shows T 2 temperature-dependent resistivity and satisfies Kadowaki- Woods relation, which is indicative of heavy-fermion behavior. Here, we present the crystal structures and physical properties of Ln(Cu,Ga) 13-x (Ln=La-Nd, Eu; x≈0.2). © 2009 American Chemical Society.

    DOI： 10.1021/cm803297q

  • 28aRL-6 Quantum criticality in β-YbAlB_4 probed by the thermal transport coefficient

    Ogura C., Machida Y., Izawa K., Kuga K., Tomita T., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   64 ( 2 )   563 - 563   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.2.3.0_563_4

  • 28aRL-5 Fe-substitution dependence of Yb valence in heavy fermion Yb(Al, Fe)B_4

    Okawa M., Nishino Y., Ishikawa T., Kuga K., Horie N., Nakatsuji S., Shin S., Matsunami M., Ishizaka K., Eguchi R., Taguchi M., Chainani Ashish, Takata Y., Yabashi M., Tamasaku K.

    Meeting Abstracts of the Physical Society of Japan   64 ( 2 )   563 - 563   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.2.3.0_563_3

  • 30aTD-5 Photoemission spectroscopy of heavy-fermion system YbAlB_4 : Electronic structure and valence estimation

    Okawa M., Nishino Y., Ishikawa T., Kuga K., Horie N., Nakatsuji S., Shin S., Matsunami M., Ishizaka K., Eguchi R., Taguchi M., Chainani Ashish, Takata Y., Yabashi M., Tamasaku K.

    Meeting Abstracts of the Physical Society of Japan   64 ( 1 )   652 - 652   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.1.3.0_652_1

  • 28aRL-3 Superconductivity and Magnetism of the Heavy Fermion System β-YbAlB_4 under Pressure

    Tomita T., Kuga K., Horie N., Matsumoto Y., Nakatsuji S., Ueda H., Matsubayashi K., Matsumoto T., Uwatoko Y.

    Meeting Abstracts of the Physical Society of Japan   64 ( 2 )   563 - 563   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.2.3.0_563_1

  • 30aTD-2 Quantum Phase Transition and Superconductivity of the Heavy Fermion System β-YbAlB_4 under Pressure

    Tomita T., Kuga K., Horie N., Matsumoto Y., Nakatsuji S., Ueda H., Matsubayashi K., Matsumoto T., Uwatoko Y.

    Meeting Abstracts of the Physical Society of Japan   64 ( 1 )   651 - 651   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.1.3.0_651_2

  • 30aTD-1 Quantum Criticality and Scaling in Thermodynamic Properties in the Heavy Fermion System β-YbAlB_4

    Matsumoto Y., Kuga K., Karaki Y., Tomita T., Machida Y., Sakakibara T., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   64 ( 1 )   651 - 651   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.1.3.0_651_1

  • 28aRL-1 Zero-Field Quantum Criticality and Non-Fermi Liquid-Fermi Liquid Crossover in the Heavy Fermi System β-YbAlB_4

    Matsumoto Y., Kuga K., Karaki Y., Tomita T., Machida Y., Sakaibara T., Shimura Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   64 ( 2 )   562 - 562   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.2.3.0_562_3

  • 30aTD-4 Impurity Effect in the Heavy Fermion Systems YbAlB_4

    Kuga K., Horie N., Matsumoto Y., Tomita T., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   64 ( 1 )   651 - 651   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.1.3.0_651_4

  • 28aRL-4 Magnetic-field-Induced Crossover in the Heavy Fermion SYstem α-YbAlB_4

    H. Naoki, Tomita T., Kuga K., Matsumoto Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   64 ( 2 )   563 - 563   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.2.3.0_563_2

  • 27pTL-8 Low temperature magnetism of Pr(CuGa)_<13>

    Shimura Y., Kuga K., Sakakibara T., Cho J. Y., Chan Julia Y.

    Meeting Abstracts of the Physical Society of Japan   64 ( 0 )   563 - 563   2009 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.1.3.0_563_4

  • 28aRL-2 Non-Fermi-liquid behavior under magnetic field along ab-plane of the quantum critical material β-YbAlB_4

    Kuga K., Matsumoto Y., Tomita T., Tokunaga M., Horie N., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   64 ( 2 )   562 - 562   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.2.3.0_562_4

  • 27pRH-7 Specific heat and ^<75>As-NQR of KFe_2As_2

    Yamada Y., Shirage P. M., Kihou K., Lee C-H., Kito H., Iyo A., Eisaki H., Kondo K., Saito T., Fukazawa H., Kohori Y., Kuga K., Matsumoto Y., Nakatsuji S., Takeshita N.

    Meeting Abstracts of the Physical Society of Japan   64 ( 0 )   545 - 545   2009 （     eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.2.3.0_545_4

  • 30aTD-3 Low Temperature Physical Properties of Heavy Fermion System α-YbAlB_4

    Naoki H., Tomita T., Kuga K., Matsumoto Y., Petrovic Cedomir, Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   64 ( 1 )   651 - 651   2009 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.64.1.3.0_651_3

  • KFe2As2の比熱及び75As-NQR

    山田佑自, 近藤健二, 齊藤拓, 深澤英人, 深澤英人, 小堀洋, 小堀洋, 久我健太郎, 松本洋介, 中辻知, 竹下直, 竹下直, SHIRAGE P. M., 木方邦宏, 木方邦宏, LEE C-H., LEE C-H., 鬼頭聖, 鬼頭聖, 伊豫彰, 伊豫彰, 永崎洋, 永崎洋

    日本物理学会講演概要集   64 ( 2 )   2009 （   ISSN:1342-8349 ）

  • Pr(CuGa)13の低温磁性

    志村恭通, 久我健太郎, 榊原俊郎, CHO J. Y., CHAN Julia Y.

    日本物理学会講演概要集   64 ( 1 )   2009 （   ISSN:1342-8349 ）

  • 26aWP-1 Low temperature transport and magnetic properties of the heavy fermion compound β-YbAlB_4

    Nakatsuji S., Kuga K., Machida Y., Matsumoto Y., Karaki Y., Tayama T., Sakakibara T., Ishimoto H.

    Meeting Abstracts of the Physical Society of Japan   63 ( 1 )   632 - 632   2008 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.63.1.3.0_632_2

  • 20aQF-4 Non-Fermi-Liquid Behavior in the Heavy Fermion System YbAlB_4 under Pressure

    Tomita T., Kuga K., Matsumoto Y., Nakatsuji S., Ueda H., Ueda Y., Matsubayashi K., Uwatoko Y.

    Meeting Abstracts of the Physical Society of Japan   63 ( 2 )   442 - 442   2008 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.63.2.3.0_442_4

  • 26aWP-3 Pressure Induced Phase Transition of Heavy Fermion System YbAlB_4

    Tomita T., Kuga K., Matsumoto Y., Nakatsuji S., Matsubayashi K., Uwatoko Y.

    Meeting Abstracts of the Physical Society of Japan   63 ( 1 )   632 - 632   2008 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.63.1.3.0_632_4

  • 20aQF-3 Thermodynamic Properties of Quantum Criticality in the Heavy Fermion System β-YbAlB_4

    Matsumoto Y., kuga K., Karaki Y., Tomita T., Machida Y., Nakatsuji S.

    Meeting Abstracts of the Physical Society of Japan   63 ( 2 )   442 - 442   2008 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    DOI： 10.11316/jpsgaiyo.63.2.3.0_442_3

  • 26aWP-2 Non-Fermi-Liquid Behavior and Sample Dependence in Pure Single Crystal of Heavy Fermion System YbAlB_4

    Kuga K., Nakatsuji S., Yonezawa S., Karaki Y., Kiuchi Y., Ichihara M., Ishimoto H., Maeno Y.

    Meeting Abstracts of the Physical Society of Japan   63 ( 1 )   632 - 632   2008 （   ISSN:1342-8349   eISSN:2189-0803 ）

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    Language：Japanese   Publisher：The Physical Society of Japan  

    DOI： 10.11316/jpsgaiyo.63.1.3.0_632_3

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Presentations

  • 価数揺動物質YbSi2における巨大ペルチェ係数 International conference

    久我　健太郎, 松波　雅治, 濱本諭*, 大浦正樹*, 竹内　恒博

    日本物理学会 第77回年次大会  ( オンライン )   2022.3  日本物理学会

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    Presentation type：Oral presentation (general)  

  • High performance and anomalous anisotropy in Yb-based thermoelectric materials International conference

    Kentaro Kuga, Masaharu Matsunami, Tsunehiro Takeuchi

    CREST「異常電子熱伝導度と異常格子熱伝導度の制御」Workshop  ( オンライン )   2021.12 

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    Presentation type：Oral presentation (general)  

  • 価数揺動物質α-YbAlB4における擬一次元的熱電特性 International conference

    久我　健太郎, 松波　雅治, 中辻知 東京大学物性研究所*, 竹内　恒博

    日本物理学会 2021年秋季大会  ( オンライン )   2021.9  日本物理学会

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  • Ag2Teの磁場下における熱電物性の挙動 International conference

    平田圭佑*, 武藤正憲*, 久我　健太郎, シン　サウラブ, 松波　雅治, 竹内　恒博

    第18回日本熱電学会学術講演会（TSJ2021）  ( オンライン )   2021.8  日本熱電学会

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    Presentation type：Oral presentation (general)  

  • 重い電子系におけるゼーベック係数の制御 International conference

    松波　雅治, 尾川史武*, 岡田真由子*, 久我　健太郎, 竹内　恒博

    第18回日本熱電学会学術講演会（TSJ2021）  ( オンライン )   2021.8  日本熱電学会

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  • 共鳴硬X線光電子分光による価数揺動系量子臨界物質alpha-YbAl1-xFexB4の電子構造研究 International conference

    久我　健太郎, 姫野良介 **, 藤原秀紀 **, 濱本諭 **, 保井晃 **, 雀部矩正 **, 柴垣善則 **, 河村直己 **, 松波　雅治, 竹内　恒博

    日本物理学会第76回年次大会  ( オンライン )   2021.3  日本物理学会

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  • 放射光光電子分光による量子臨界物質YbCo2Ge4の4f基底状態軌道対称性と混成効果の研究 International conference

    久我　健太郎, 濱本諭 **, 中谷泰博 **, 金井惟奈 **, 藤原秀紀 **, 青山雄一 **, 関山明 **, 東谷篤志 **, 門野利治 **, 今田真 **

    日本物理学会2020年秋季大会  ( オンライン )   2020.9  日本物理学会

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  • Substitution Effect on Thermoelectric Properties of CePd3 International conference

    Fumitake Ogawa Energy Materials Lab.**, Kentaro Kuga, Masaharu Matsunami, Tsunehiro Takeuchi

    Materials Research Meeting 2019 (MRM2019),  ( Yokohama, Japan, )   2019.12 

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  • Yb5Si3における不均一価数揺動状態の観測 International conference

    松波　雅治, 久我　健太郎, 飯塚　拓也, 竹内　恒博

    日本物理学会 2019年秋季大会  ( 岐阜大学，柳戸キャンパス )   2019.9  日本物理学会

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Grant-in-Aid for Scientific Research