Updated on 2021/12/20

写真a

 
KOBAYASHI Kaya
 
Organization
Research Institute for Interdisciplinary Science Associate Professor
Position
Associate Professor
External link

Degree

  • 博士(工学) ( 東京大学 )

Research Areas

  • Natural Science / Magnetism, superconductivity and strongly correlated systems

  • Natural Science / Semiconductors, optical properties of condensed matter and atomic physics

Education

  • The University of Tokyo   工学系研究科   物理工学専攻

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    Country: Japan

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  • The University of Tokyo   工学系研究科   物理工学専攻

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    Country: Japan

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  • The University of Tokyo   工学部   物理工学科

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    Country: Japan

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Professional Memberships

Committee Memberships

  • 日本物理学会   第77期男女共同参画推進委員会委員  

    2021.4   

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    Committee type:Academic society

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  •   応用物理学関係連合講演会 現地実行委員  

    2014.3   

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  •   日本物理学会領域7 運営委員  

    2013.10 - 2014.9   

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    Committee type:Academic society

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  •   応用物理学関係連合講演会 現地実行委員  

    2007.3   

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    Committee type:Academic society

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Papers

  • Current-induced magnetization caused by crystal chirality in nonmagnetic elemental tellurium Reviewed

    Tetsuya Furukawa, Yuta Watanabe, Naoki Ogasawara, Kaya Kobayashi, Tetsuaki Itou

    Physical Review Research   3 ( 2 )   2021.5

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

    DOI: 10.1103/PhysRevResearch.3.023111

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevResearch.3.023111/fulltext

  • Hole doping and chemical pressure effects on the strong coupling superconductor PdTe

    Li Chen, Ando Ide, Harald O. Jeschke, Kaya Kobayashi

    Physical Chemistry Chemical Physics   23 ( 23 )   13331 - 13337   2021

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    <p>Superconducting transition temperature <italic>T</italic>c shows a dependence on an angle formed between Te–Pd–Te in a PdTe6 octahedron (inset).</p>

    DOI: 10.1039/d1cp01071a

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  • Superconductivity in Bi2−x Sb x Te3−y Se y (x = 1.0 and y = 2.0) under pressure Reviewed

    Tong He, Xiaofan Yang, Tomoya Taguchi, Lei Zhi, Takafumi Miyazaki, Kaya Kobayashi, Jun Akimitsu, Hirofumi Ishii, Yen-Fa Liao, Hidenori Goto, Ritsuko Eguchi, Yoshihiro Kubozono

    Journal of Physics: Condensed Matter   32 ( 46 )   465702 - 465702   2020.11

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    Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing  

    DOI: 10.1088/1361-648x/abaad2

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    Other Link: https://iopscience.iop.org/article/10.1088/1361-648X/abaad2/pdf

  • Time-reversal invariant and fully gapped unconventional superconducting state in the bulk of the topological compound Nb0.25Bi2Se3 Reviewed

    Debarchan Das, K. Kobayashi, M. P. Smylie, C. Mielke, T. Takahashi, K. Willa, J.-X. Yin, U. Welp, M. Z. Hasan, A. Amato, H. Luetkens, Z. Guguchia

    Physical Review B   2020.10

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    DOI: 10.1103/PhysRevB.102.134514

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  • Magnetotransport properties of tellurium under extreme conditions Reviewed

    Kazuto Akiba, Kaya Kobayashi, Tatsuo C. Kobayashi, Ryo Koezuka, Atsushi Miyake, Jun Gouchi, Yoshiya Uwatoko, Masashi Tokunaga

    Physical Review B   101 ( 24 )   2020.6

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    © 2020 American Physical Society. This study investigates the transport properties of a chiral elemental semiconductor tellurium (Te) under magnetic fields and pressure. Application of hydrostatic pressure reduces the resistivity of Te, while its temperature dependence remains semiconducting up to 4 GPa, contrary to recent theoretical and experimental studies. Application of higher pressure causes structural as well as semiconductor-metal transitions. The resulting metallic phase above 4 GPa exhibits superconductivity at 2 K along with a noticeable linear magnetoresistance effect. On the other hand, at ambient pressure, we identified metallic surface states on the as-cleaved (1010) surfaces of Te. The nature of these metallic surface states has been systematically studied by analyzing quantum oscillations observed in high magnetic fields. We clarify that a well-defined metallic surface state exists not only on chemically etched samples that were previously reported, but also on as-cleaved ones.

    DOI: 10.1103/PhysRevB.101.245111

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  • Optical signatures of phase transitions and structural modulation in elemental tellurium under pressure Reviewed

    Diego Rodriguez, Alexander A. Tsirlin, Tobias Biesner, Teppei Ueno, Takeshi Takahashi, Kaya Kobayashi, Martin Dressel, Ece Uykur

    Physical Review B   2020.5

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    DOI: 10.1103/PhysRevB.101.174104

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  • Superconductivity in 5d transition metal Laves phase SrIr2 Reviewed

    R Horie, K Horigane, S Nishiyama, M Akimitsu, K Kobayashi, S Onari, T Kambe, Y Kubozono, J Akimitsu

    Journal of Physics: Condensed Matter   32 ( 17 )   175703 - 175703   2020.4

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    © 2020 IOP Publishing Ltd. We report here the superconducting properties of a Laves phase superconductor SrIr2, which has a cubic MgCu2 structure. SrIr2 is a type-II superconductor, with a T c of 5.9 K. The estimated superconducting parameters of lower critical field µ 0 H c1 and upper critical field µ 0 H c2, coherence length ξ(0), penetration depth λ(0) and Ginzburg-Landau (GL) parameter κ(0) are approximately µ 0 H c1 = 101 Oe, µ 0 H c2(0) = 5.9 T, ξ(0) = 7.47 nm, λ(0) = 237 nm, and κ(0) = 31.7, respectively. The specific-heat data indicate that SrIr2 is a strong-coupling superconductor because the value of ΔC/γT c is approximately 1.71, which is larger than the value of 1.43 that is expected from the BCS theory. The physical properties obtained in this study are explained well by theoretical calculations including spin-orbit coupling (SOC). This result indicates that the physical properties of SrIr2 are strongly affected by the presence of SOC.

    DOI: 10.1088/1361-648x/ab6a2e

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    Other Link: https://iopscience.iop.org/article/10.1088/1361-648X/ab6a2e/pdf

  • Two Linear Regimes in Optical Conductivity of a Type-I Weyl Semimetal: The Case of Elemental Tellurium Reviewed

    Diego Rodriguez, Alexander A. Tsirlin, Tobias Biesner, Teppei Ueno, Takeshi Takahashi, Kaya Kobayashi, Martin Dressel, Ece Uykur

    Physical Review Letters   2020.3

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    DOI: 10.1103/PhysRevLett.124.136402

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  • μSR Study of the Magnetic State in Hole and Electron Doped Sr2IrO4

    S. Tsunoda, K. Horigane, H. Okabe, K. Machida, M. Akimitsu, K. Kawashima, R. Horie, K. Kobayashi, A. Koda, R. Kadono, J. Akimitsu

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

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

    DOI: 10.7566/jpscp.30.011145

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  • Superconducting Properties of AgSnSe2 Studied by 77Se-NMR and 119Sn-NMR

    K. Watanabe, Y. Naijo, K. Hada, T. Furukawa, T. Itou, T. Ueno, K. Kobayashi, J. Akimitsu

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

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

    DOI: 10.7566/jpscp.30.011057

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  • Nodeless superconducting gap in the candidate topological superconductor Sn1−xInxTe for x=0.7 Reviewed

    M. P. Smylie, Kaya Kobayashi, T. Takahashi, C. Chaparro, A. Snezhko, W.-K. Kwok, U. Welp

    Physical Review B   2020.3

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    DOI: 10.1103/PhysRevB.101.094513

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  • Superconducting 3R-Ta1+xSe2 with Giant In-Plane Upper Critical Fields Reviewed

    Yuki Tanaka, Hideki Matsuoka, Masaki Nakano, Yue Wang, Sana Sasakura, Kaya Kobayashi, Yoshihiro Iwasa

    Nano Letters   20 ( 3 )   1725 - 1730   2020.3

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

    DOI: 10.1021/acs.nanolett.9b04906

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  • Unusual electronic state of Sn in AgSnSe2 Reviewed

    Y. Naijo, K. Hada, T. Furukawa, T. Itou, T. Ueno, K. Kobayashi, I. I. Mazin, H. O. Jeschke, J. Akimitsu

    Physical Review B   101 ( 7 )   075134   2020.2

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    DOI: 10.1103/PhysRevB.101.075134

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  • Superconducting behavior of a new metal iridate compound, SrIr<inf>2</inf>, under pressure Reviewed

    Xiaofan Yang, Huan Li, Tong He, Tomoya Taguchi, Yanan Wang, Hidenori Goto, Ritsuko Eguchi, Rie Horie, Kazumasa Horigane, Kaya Kobayashi, Jun Akimitsu, Hirofumi Ishii, Yen Fa Liao, Hitoshi Yamaoka, Yoshihiro Kubozono

    Journal of Physics Condensed Matter   32 ( 2 )   2020

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    © 2019 IOP Publishing Ltd. Herein, we investigated the pressure dependence of electric transport in a new type of superconducting metal iridate compound, SrIr2, that exhibits a superconducting transition temperature, T c, as high as 6.6 K at ambient pressure, in order to complete the T c-pressure (p ) phase diagram. Very recently, this sample's superconductivity was discovered by our group, but the superconducting behavior has not yet been clarified under pressure. In this study, we fully investigated this sample's superconductivity in a wide pressure range. The T c value decreased with an increase in pressure, but the onset superconducting transition temperature, (R-T plot), increased above a pressure of 8 GPa, indicating an unconventional superconductivity different from a BCS-type superconductor. The magnetic field dependence of electric resistance (R) against temperature (R-T plot) recorded at 7.94 and 11.3 GPa suggested an unconventional superconductivity, followed by a p -wave polar model, supporting the deviation from a simple s-wave pairing. Moreover, we fully investigated the pressure dependence of crystal structure in SrIr2 and discussed the correlation between superconductivity and crystal structure. This is the first systematic study on superconducting behavior of a new type of metal iridate compound, MIr2 (M: alkali-earth metal atom), under pressure.

    DOI: 10.1088/1361-648X/ab4605

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  • Fermi level tuning of Ag-doped Bi2Se3 topological insulator Reviewed

    Eri Uesugi, Takaki Uchiyama, Hidenori Goto, Hiromi Ota, Teppei Ueno, Hirokazu Fujiwara, Kensei Terashima, Takayoshi Yokoya, Fumihiko Matsui, Jun Akimitsu, Kaya Kobayashi, Yoshihiro Kubozono

    Scientific Reports   9 ( 1 )   2019.12

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1038/s41598-019-41906-7

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    Other Link: http://www.nature.com/articles/s41598-019-41906-7

  • Superconductivity of carbides

    Kaya Kobayashi, Kazumasa Horigane, Rie Horie, Jun Akimitsu

    Physics and Chemistry of Carbon-Based Materials: Basics and Applications   149 - 209   2019.3

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    Publishing type:Part of collection (book)  

    © Springer Nature Singapore Pte Ltd. 2019. Carbon-based superconductors can be roughly categorized into two groups. The first includes relatively new superconductors, such as boron-doped diamond, graphite-intercalated compounds (GIC), carbon nanotube (CNT) superconductors and fullerene superconductors. Here, we review relatively "old materials," which are materials that can be described within the "BCS (Bardeen-Cooper-Schrieffer) frame." The contents of this chapter are as follows: 1. MX-type compounds (B1-type superconductors and SiC) 2. MC2 compounds (YC2 and LaC2) 3. Ln2C3 (La2C3 and Y2C3) 4. Boron carbide (RNi2B2C and YB2C2) We introduce the present experimental and theoretical understanding of carbonbased superconductors.

    DOI: 10.1007/978-981-13-3417-7_6

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  • Crystal structure and superconducting properties of KSr2Nb3O10 Reviewed

    T. Kawaguchi, K. Horigane, Y. Itoh, K. Kobayashi, R. Horie, T. Kambe, J. Akimitsu

    Physica B: Condensed Matter   536   830 - 832   2018.5

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    We performed X-ray diffraction (XRD) and DC magnetic susceptibility measurements to elucidate the crystal structure and superconducting properties of KSr2Nb3O10. From the diffraction pattern indexing, it was found that KSr2Nb3O10 crystallizes with monoclinic symmetry, space group P21/m(11). We succeeded in preparing high temperature (HT) and low temperature (LT) phases of KSr2Nb3O10 powder samples synthesized by a conventional solid state reaction and an ion-exchange reaction, respectively. Superconductivity was observed at 4 K by Li intercalation and it was found that the superconducting volume fraction of the LT phase (~ 1.4%) is clearly larger than that of the HT phase (0.07%).

    DOI: 10.1016/j.physb.2017.09.060

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  • Enhanced superconducting transition temperatures in the rocksalt-type superconductors In1-xSnxTe (x≤0.5) ENHANCED SUPERCONDUCTING TRANSITION ... KOBAYASHI, AI, JESCHKE, and AKIMITSU Reviewed

    Kaya Kobayashi, Yukio Ai, Harald O. Jeschke, Jun Akimitsu

    Physical Review B   97 ( 10 )   2018.3

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    We investigate superconductivity in In1-xSnxTe (x≤0.5) synthesized at high pressures of up to 2 GPa and observe an enhancement of the superconducting transition temperature Tc for increasing tin concentration x. These compounds have not been accessible in rocksalt structure via conventional ambient pressure synthesis. While the lattice constant smoothly increases with x, Tc saturates around x=0.4. Electronic structure calculations indicate that the Tc modulation is brought on by the change of the density of states in the vicinity of the Fermi energy [N(EF)]. However, differences between the calculated N(EF) and the observed electronic specific-heat coefficient indicate that the phonon dispersion plays an important role in the system and that the mechanism of superconductivity may not be the same in the entire doping range.

    DOI: 10.1103/PhysRevB.97.104511

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  • Pressure-induced superconductivity in AgxBi2-xSe3 Reviewed

    Tong He, Xiaofan Yang, Takahiro Terao, Takaki Uchiyama, Teppei Ueno, Kaya Kobayashi, Jun Akimitsu, Takafumi Miyazaki, Takumi Nishioka, Koji Kimura, Kouichi Hayashi, Naohisa Happo, Hitoshi Yamaoka, Hirofumi Ishii, Yen-Fa Liao, Hiromi Ota, Hidenori Goto, Yoshihiro Kubozono

    Physical Review B   97 ( 10 )   2018.3

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    We investigated the pressure dependence of electric transport and crystal structure of Ag-doped Bi2Se3. In the sample prepared by Ag doping of Bi2Se3, the Bi atom was partially replaced by Ag, i.e., Ag0.05Bi1.95Se3. X-ray diffraction patterns of Ag0.05Bi1.95Se3 measured at 0-30 GPa showed three different structural phases, with rhombohedral, monoclinic, and tetragonal structures forming in turn as pressure increased, and structural phase transitions at 8.8 and 24 GPa. Ag0.05Bi1.95Se3 showed no superconductivity down to 2.0 K at 0 GPa, but under pressure, superconductivity suddenly appeared at 11 GPa. The magnetic field (H) dependence of the superconducting transition temperature Tc was measured at 11 and 20.5 GPa, in order to investigate whether the pressure-induced superconducting phase is explained by either p-wave polar model or s-wave model.

    DOI: 10.1103/PhysRevB.97.104503

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  • Magnetic phase diagram of S r2-x L axIr O4 synthesized by mechanical alloying Reviewed

    K. Horigane, M. Fujii, H. Okabe, K. Kobayashi, R. Horie, H. Ishii, Y. F. Liao, Y. Kubozono, A. Koda, R. Kadono, J. Akimitsu

    Physical Review B   97 ( 6 )   2018.2

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    We report the crystal structure and physical properties of Sr2-xLaxIrO4 synthesized by mechanical alloying. The magnetic transition temperature TN and electrical resistivity decreased with increasing La doping, consistent with previous studies involving single-crystalline samples. We also identified the relationship between TN and tetragonal distortion (c/a) in this system. This result suggests that the magnetism of the Sr214 system is strongly correlated with its crystal structure. Zero-field muon spin rotation/relaxation studies revealed that short-range antiferromagnetic ordering is realized in Sr1.9La0.1IrO4
    also, the spin-glass state is stabilized in the low-temperature region. The Ir moment estimated from the longitudinal field μSR results is 0.045μB, ten times smaller than that of Sr2IrO4 (∼0.4μB), indicating that electrons are introduced into the Ir atoms.

    DOI: 10.1103/PhysRevB.97.064425

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  • Determination of the local structure of Sr2−xMxIrO4 (M = K, La) as a function of doping and temperature Reviewed

    Kensei Terashima, Eugenio Paris, Eduardo Salas-Colera, Laura Simonelli, Boby Joseph, Takanori Wakita, Kazumasa Horigane, Masanori Fujii, Kaya Kobayashi, Rie Horie, Jun Akimitsu, Yuji Muraoka, Takayoshi Yokoya, Naurang Lal Saini

    Physical Chemistry Chemical Physics   20 ( 36 )   23783 - 23788   2018

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    The local structure of correlated spin-orbit insulator Sr2-xMxIrO4 (M = K, La) has been investigated by Ir L-3-edge extended X-ray absorption fine structure measurements. The measurements were performed as a function of temperature for different dopings induced by substitution of Sr with La or K. It is found that Ir-O bonds have strong covalency and they hardly show any change across the Neel temperature. In the studied doping range, neither Ir-O bonds nor their dynamics, measured by their mean square relative displacements, show any appreciable change upon carrier doping, indicating the possibility of nanoscale phase separation in the doped system. On the other hand, there is a large increase of the static disorder in Ir-Sr correlation, larger for K doping than La doping. Similarities and differences with respect to the local lattice displacements in cuprates are briefly discussed.

    DOI: 10.1039/C8CP03756F

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  • Observation of current-induced bulk magnetization in elemental tellurium Reviewed

    Tetsuya Furukawa, Yuri Shimokawa, Kaya Kobayashi, Tetsuaki Itou

    NATURE COMMUNICATIONS   8   2017.10

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

    The magnetoelectric effect in bulk matter is of growing interest both fundamentally and technologically. Since the beginning of the century, the magnetoelectric effect has been studied intensively in multiferroic materials. However, magnetoelectric phenomena in materials without any (anti-) ferroic order remain almost unexplored. Here we show the observation of a new class of bulk magnetoelectric effect, by revisiting elemental trigonal tellurium. We demonstrate that elemental tellurium, which is a nonmagnetic semiconductor, exhibits current-induced magnetization. This effect is attributed to spin splitting of the bulk band owing to the lack of inversion symmetry in trigonal tellurium. This finding highlights magnetoelectricity in bulk matter driven by moving electrons without any (anti-) ferroic order. Notably, current-induced magnetization generates a magnetic field that is not circular around but is parallel to the applied current; thus, this phenomenon opens a new area of magnetic field generation beyond Ampere's law that may lead to industrial applications.

    DOI: 10.1038/s41467-017-01093-3

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  • The electronic structure of Ag1-xSn1+xSe2 (x=0.0, 0.1, 0.2, 0.25 and 1.0) Reviewed

    Takanori Wakita, Eugenio Paris, Kaya Kobayashi, Kensei Terashima, Muammer Yasin Hacisalihoglu, Teppei Ueno, Federica Bondino, Elena Magnano, Igor Pis, Luca Olivi, Jun Akimitsu, Yuji Muraoka, Takayoshi Yokoya, Naurang L. Saini

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS   19 ( 39 )   26672 - 26678   2017.10

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    We have studied the valence electronic structure of Ag1-xSn1+xSe2 (x = 0.0, 0.1, 0.2, 0.25) and SnSe (x = 1.0) by a combined analysis of X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS) measurements. Both XAS and XPS reveal an increase in electron carriers in the system with x (i.e. excess Sn concentration) for 0 &lt;= x &lt;= 0.25. The core-level spectra (Sn 3d, Ag 3d and Se 3d) show that the charge state of Ag is almost 1+, while that of of Sn splits into Sn2+ and Sn4+ (providing clear evidence of valence skipping for the first time) with a concomitant splitting of Se into Se2- and Se2-delta states. The x dependence of the split components in Sn and Se together with the Se-K edge XAS reveals that the Se valence state may have an essential role in the transport properties of this system.

    DOI: 10.1039/c7cp05369j

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  • Evolution of the remnant Fermi-surface state in the lightly doped correlated spin-orbit insulator Sr2-xLaxIrO4 Reviewed

    K. Terashima, M. Sunagawa, H. Fujiwara, T. Fukura, M. Fujii, K. Okada, K. Horigane, K. Kobayashi, R. Horie, J. Akimitsu, E. Golias, D. Marchenko, A. Varykhalov, N. L. Saini, T. Wakita, Y. Muraoka, T. Yokoya

    PHYSICAL REVIEW B   96 ( 4 )   2017.7

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

    The electronic structure of the lightly electron-doped correlated spin-orbit insulator Sr2IrO4 has been studied by angle-resolved photoelectron spectroscopy. We have observed the coexistence of a lower Hubbard band and an in-gap band; the momentum dependence of the latter traces that of the band calculations without on-site Coulomb repulsion. The in-gap state remained anisotropically gapped in all observed momentum areas, forming a remnant Fermi-surface state, evolving towards the Fermi energy by carrier doping. These experimental results show a striking similarity with those observed in deeply underdoped cuprates, suggesting the common nature of the nodal liquid states observed in both compounds.

    DOI: 10.1103/PhysRevB.96.041106

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    Other Link: http://orcid.org/0000-0001-6707-6964

  • Unusual upper critical field behavior in Nb-doped bismuth selenides Reviewed

    Kaya Kobayashi, T. Ueno, H. Fujiwara, T. Yokoya, J. Akimitsu

    Physical Review B   95 ( 18 )   2017.5

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physical Society  

    We investigate superconductivity in the candidate topological superconductor NbxBi2Se3 from x=0 to 1. We observe superconductivity for all x&gt
    0 with a superconducting transition temperature TC∼ 3 K similar to that reported in Cu- and Sr-intercalated Bi2Se3. Structurally, for small x we find introduction of Nb modifies the Bi2Se3 separation while for larger x the system is driven to the BiSe structure. While all compounds are found to be superconducting, two distinct behaviors for the upper critical field Hc2 are observed. From photoemission spectroscopy we find that the enhanced Hc2 corresponds to compounds with a low surface Dirac point energy (-0.67 eV) relative to the Fermi level
    in absolute scale this value is lower than previously reported superconductors in this materials family. We comment on the utility of this system for the study of topological superconductivity in a new structure type combining a doping (Bi2 type) layer and layers with topologically protected gapless state (Bi2Se3 type).

    DOI: 10.1103/PhysRevB.95.180503

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    Other Link: http://orcid.org/0000-0001-6707-6964

  • The quest for new chalcogenide superconductors

    Kobayashi Kaya, Ueno Teppei, Akimitsu Jun

    Meeting Abstracts of the Physical Society of Japan   71   2040 - 2040   2016

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    Language:Japanese   Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.71.2.0_2040

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  • Structure and superconductivity in KSr2Nb3O10

    Kobayashi Kaya, Kawaguchi T., Horigane K., Akimitsu J.

    Meeting Abstracts of the Physical Society of Japan   71   2235 - 2235   2016

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    Language:Japanese   Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.71.2.0_2235

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  • Study of electronic states on Sr2-xLaxIrO4 (x = 0.04, 0.08) : Angle-resolved photoelectron spectroscopy

    Terashima K., Sunagawa M., Fujiwara H., Fujii M., Horigane K., Kobayashi K., Horie R., Akimitsu J., Muraoka Y., Yokoya T.

    Meeting Abstracts of the Physical Society of Japan   71   1791 - 1791   2016

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    Language:Japanese   Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.71.2.0_1791

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  • Metallic Binary Copper Chalcogenides with Orthorhombic Layered Structure Reviewed

    Kaya Kobayashi, Shinya Kawamoto, Jun Akimitsu

    Materials Research Society Symposium Proceedings   1726   2015

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Materials Research Society  

    Chalcogenide materials have regained attention after the recent recognition of the compatibility of transition metal dichalcogenides with graphene. Additionally, there has been a recent appreciation for the rich variety of properties they support due to the anomalies in the materials' intrinsic band structure. These materials generally have layered structures and weak interlayer connection through the chalcogen layer and its van der Waals type bonding. We have synthesized orthorhombic copper telluride and measured its electrical transport properties. The results of these measurements reveal that the conduction is metallic in both the in-plane and out-of-plane directions. The range of stability of this structure is examined along with the lattice constants. The independence of the resistivity in samples to changes in excess copper indicates that the transport is essentially within the conducting planes. This result shows that the material hosts two-dimensional character likely due to its covalent interlayer bonding.

    DOI: 10.1557/opl.2015.467

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    Other Link: http://orcid.org/0000-0001-6707-6964

  • Investigation of Mechanical Agitation in the Dynamics of the Electrochemical Growth of Organic Crystals in a Nanoliter Cell Reviewed

    Kaya Kobayashi

    ADVANCED MATERIALS INTERFACES   1 ( 6 )   2014.9

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:WILEY-BLACKWELL  

    DOI: 10.1002/admi.201400096

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  • Anomalous local spin susceptibilities in noncentrosymmetric La2C3 superconductor Reviewed

    Anton Potocnik, Peter Jeglic, Kaya Kobayashi, Kenji Kawashima, Saori Kuchida, Jun Akimitsu, Denis Arcon

    PHYSICAL REVIEW B   90 ( 10 )   2014.9

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    We report on La-139 and C-13 nuclear magnetic resonance (NMR) study of noncentrosymmetric superconductor La2C3 with superconducting critical temperature T-c = 11.8 K. In the normal state La-139 NMR spectra show a characteristic quadrupole polycrystalline broadening yielding a quadrupole frequency nu(Q) = 3.1 MHz and a very large shift of similar to 3000 ppm. A significant part of this shift arises from the Van Vleck-like susceptibility as a result of a sizable spin-orbit coupling. In the superconducting phase La2C3 shows abnormal behavior that dramatically deviates from the conventional s-wave superconductors. Namely, (i) La-139 and C-13 NMR shifts in the superconducting state do not change from their normal-state values, and (ii) the La-139 spin-lattice relaxation rate is strongly enhanced below T-c. Such unconventional response in the local static and dynamic spin susceptibilities is discussed in terms of possible mixture of spin-singlet and spin-triplet Cooper pairs, which is promoted by the asymmetric spin-orbit coupling in the system without the center of inversion.

    DOI: 10.1103/PhysRevB.90.104507

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  • Observation of Orbital Resonance Hall Effect in (TMTSF)(2)ClO4 Reviewed

    Kaya Kobayashi, H. Satsukawa, J. Yamada, T. Terashima, S. Uji

    PHYSICAL REVIEW LETTERS   112 ( 11 )   2014.3

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    We report the observation of a Hall effect driven by orbital resonance in the quasi-1-dimensional (q1D) organic conductor (TMTSF)(2)ClO4. Although a conventional Hall effect is not expected in this class of materials due to their reduced dimensionality, we observed a prominent Hall response at certain orientations of the magnetic field B corresponding to lattice vectors of the constituent molecular chains, known as the magic angles (MAs). We show that this Hall effect can be understood as the response of conducting planes generated by an effective locking of the orbital motion of the charge carriers to the MA driven by an electron-trajectory resonance. This phenomenon supports a class of theories describing the rich behavior of MA phenomena in q1D materials based on altered dimensionality. Furthermore, we observed that the effective carrier density of the conducting planes is exponentially suppressed in large B, which indicates possible density wave formation.

    DOI: 10.1103/PhysRevLett.112.116805

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  • Magnetic Properties of Chalcopyrite Cu1−xFeS2 at Low Temperatures Reviewed

    K. Kobayashi, Y. Azuma, K. Kawashima, K. Horigane, M. Akaki, M. Tokunaga, J. Akimitsu

    Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013)   2014.1

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    DOI: 10.7566/JPSCP.3.017020

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  • Instability of charge ordered states probed in mesoscopic theta-(BEDT-TTF)(2)RbZn(SCN)(4) crystals Reviewed

    Kaya Kobayashi, Naoki Uchida

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 9, NO 5   9 ( 5 )   1167 - 1170   2012

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    We developed a technique to grow organic crystals in nanoliter cells compatible with subsequent electrical transport measurements. The crystals grown in this technique have thickness less than 1 mu m due to the confined growth condition. Here, a q2D organic conductor that shows a metal-insulator transition in low temperature is grown. Resistivity (rho) measurements as a function of temperature (T) showed no discontinuity in d rho/dT in contrast to the reported behavior in bulk crystals. Instead, rho displays a broad increase in the vicinity of 150 K. The nonlinear behavior of IV curves observed obeys a power law for most of the T range. A high bias voltage did not change the broad increase of resistivity between 140 and 160 K. The color plot demonstrates that the CO state is stable against biasing by an electric field. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.201100648

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  • Growth and observation of micro-organic crystals in two-dimensional glass nanovolume cell Reviewed

    Kaya Kobayashi, Hiroko Koyama, Kodai Ishikura, Toshiyuki Mitsui

    APPLIED PHYSICS LETTERS   93 ( 14 )   2008.10

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    A simple type of glass cell to control the organic crystal growth in microsize by electrochemical method is presented. We fabricated growth cells with electrodes patterned by photolithograph and nanoliter volume. They have several merits for growth of organic conductors in microsize, including confined growth volume, observable growth space, rapid growth cycle relative to conventional methods, and compatibility with existing microfabrication techniques. The real time observation of the crystal growth was performed. The results are discussed in terms of the growth mechanism, suggesting a possibility of another microscopic view of crystal growth. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2999583]

    DOI: 10.1063/1.2999583

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  • Electric-field effect on the angle-dependent magnetotransport properties of quasi-one-dimensional conductors Reviewed

    K Kobayashi, M Saito, E Ohmichi, T Osada

    PHYSICAL REVIEW LETTERS   96 ( 12 )   2006.3

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    We report a novel electric field effect on angular dependent magnetotransport in quasi-one-dimensional layered conductors with a pair of sheetlike Fermi surfaces. Under tilted magnetic fields and additional interlayer electric fields, semiclassical electron orbits on two Fermi sheets become periodic at different magnetic field orientations. This causes double splitting of the Lebed's commensurability resonance in interlayer transport, and the amount of splitting allows us to estimate the Fermi velocity directly. We have successfully demonstrated this effect in the organic conductor alpha-(BEDT-TTF)(2)KHg(SCN)(4).

    DOI: 10.1103/PhysRevLett.96.126601

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  • Electric-Field Effect on the Angle-Dependent Magnetotransport Properties of Quasi-One-Dimensional Conductors Reviewed

    Phys. Rev. Lett.   2006

  • Quantum features of angular dependent magnetoresistance oscillations in quasi-two-dimensional conductors near high magnetic field quantum limit Reviewed

    K Kobayashi, T Osada

    SYNTHETIC METALS   155 ( 3 )   670 - 673   2005.12

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    We report novel features of angular dependent magnetoresistance oscillations (AMROs) observed in strong magnetic fields where only a few Landau levels are occupied. In order to realize this "near-quantum-limit" in real Q2D systems, we have chosen GaAs/AlGaAs semiconductor superlattices for AMRO experiments. Near the quantum limit, the peak position of AMRO slightly depends on field strength, and it jumps synchronizing Shubnikov-de Haas peaks. AMRO disappears when the parallel field component exceeds a certain value which gives a broad local minimum of interlayer resistance. The observed features are hardly expected from the conventional picture based on the semiclassical Fermi surface topological effect ignoring Landau quantization. We have successfully explained these new features by the quantum mechanical picture which evaluates interlayer conductivity from magnetic eigen states using the Kubo formula. This quantum picture gives the most general and complete description of AMRO in Q2D conductors. (C) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.synthmet.2005.08.025

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  • Quantum features of angular dependent magnetoresistance oscillations in quasi-two-dimensional conductors near high magnetic field quantum limit Reviewed

    K Kobayashi, T Osada

    SYNTHETIC METALS   155 ( 3 )   670 - 673   2005.12

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    We report novel features of angular dependent magnetoresistance oscillations (AMROs) observed in strong magnetic fields where only a few Landau levels are occupied. In order to realize this "near-quantum-limit" in real Q2D systems, we have chosen GaAs/AlGaAs semiconductor superlattices for AMRO experiments. Near the quantum limit, the peak position of AMRO slightly depends on field strength, and it jumps synchronizing Shubnikov-de Haas peaks. AMRO disappears when the parallel field component exceeds a certain value which gives a broad local minimum of interlayer resistance. The observed features are hardly expected from the conventional picture based on the semiclassical Fermi surface topological effect ignoring Landau quantization. We have successfully explained these new features by the quantum mechanical picture which evaluates interlayer conductivity from magnetic eigen states using the Kubo formula. This quantum picture gives the most general and complete description of AMRO in Q2D conductors. (C) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.synthmet.2005.08.025

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  • Electric field effect on vertical magnetotransport in multilayer systems under tilted magnetic fields Reviewed

    K Kobayashi, M Saito, E Ohmichi, T Osada

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   22 ( 1-3 )   385 - 388   2004.4

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    We have investigated a new electric field effect on magnetotransport in the multilayer systems where each layer is highly anisotropic. Under tilted magnetic fields, the resonant increase of interlayer conduction occurs when open electron orbits become periodic in k-space. The interlayer electric fields tilt the open orbits on two sheetlike Fermi surfaces in the different way, causing the split of the resonance. Using an organic conductor alpha-(BEDT-TTF)(2)KHg(SCN)(4), we have successfully proved the above scenario experimentally. (C) 2003 Published by Elsevier B.V.

    DOI: 10.1016/j.physe.2003.12.027

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  • Electric field effect on vertical magnetotransport in multilayer systems under tilted magnetic fields Reviewed

    K Kobayashi, M Saito, E Ohmichi, T Osada

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   22 ( 1-3 )   385 - 388   2004.4

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    We have investigated a new electric field effect on magnetotransport in the multilayer systems where each layer is highly anisotropic. Under tilted magnetic fields, the resonant increase of interlayer conduction occurs when open electron orbits become periodic in k-space. The interlayer electric fields tilt the open orbits on two sheetlike Fermi surfaces in the different way, causing the split of the resonance. Using an organic conductor alpha-(BEDT-TTF)(2)KHg(SCN)(4), we have successfully proved the above scenario experimentally. (C) 2003 Published by Elsevier B.V.

    DOI: 10.1016/j.physe.2003.12.027

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  • Tunneling picture of interlayer magnetotransport in multilayer systems Reviewed

    T Osada, M Kuraguchi, K Kobayashi, E Ohmichi

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   18 ( 1-3 )   200 - 201   2003.5

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    Interlayer magnetatransport of multilayer systems has been generally studied. In multilayer systems with weak interlayer coupling, interlayer conduction is mainly dominated by single tunneling process between neighboring layers. The selection rule and probability of single interlayer tunneling are controlled by orientation and strength of magnetic fields. This tunneling model gives the most general explanation of most of the magnetoresistance angular effects observed in Q2D or Q1D layered conductors. The existence of the Fermi surface is not necessary for appearance of them. This model can also be applied to the modified angular effects under strong electric fields. (C) 2002 Published by Elsevier Science B.V.

    DOI: 10.1016/S1386-9477(02)00965-7

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  • Growth and transport measurement of (TMTSF)(2)PF6/(TMTSF)(2)ClO4 hetero-junctions Reviewed

    K Kobayashi, E Ohmichi, T Osada

    SYNTHETIC METALS   135 ( 1-3 )   679 - 680   2003.4

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    In order to study the mesoscopic effects of SDW systems, we have tried fabrication of organic hetero junctions. We used a (TMTSF)(2)PF6 or (TMTSF)(2)ClO4 single crystal itself as an electrode in the conventional electrochemical crystal growth, and overgrew (TMTSF)(2)ClO4 or (TMTSF)(2)PF6 on it. We successfully obtained (TMTSF)(2)PF6/(TMTSF)(2)ClO4 single crystal junctions, which is an elementary structure to fabricate mesoscopic SDW systems. We confirmed that the overgrown part of this metal/SDW junction shows the normal bulk properties. This fact suggests that epitaxial growth was successfully realized. We also present a model for the SDW transition in very thin Q1D conductors with finite number of I D chains as a mesoscopic SDW system.

    DOI: 10.1016/S0379-6779(02)00780-4

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  • Influence of interlayer and interchain coherence on magnetoresistance angular effects in Q1D conductors Reviewed

    T Osada, K Kobayashi, E Ohmichi

    SYNTHETIC METALS   135 ( 1-3 )   653 - 654   2003.4

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    The quantum tunneling picture of interlayer magnetotransport in quasi-one-dimensional conductors has been developed and applied to the problem of incoherent transport. Even in the systems having no 'interlayer' coherence, where in-plane scattering happens much oftener than interlayer tunneling, all angular effects (Lebed resonance, Danner-Chaikin: oscillation, the third angular effect) appear except the peak effect. On the other hand, in the systems having weak 'interchain' coherence, only the Lebed resonances with small indices survive.

    DOI: 10.1016/S0379-6779(02)00763-4

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  • Electric field effect on magnetoresistance angular effects in low-dimensional organic conductors Reviewed

    K Kobayashi, E Ohmichi, T Osada

    SYNTHETIC METALS   133   71 - 73   2003.3

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    The change of magnetoresistance angular effects induced by strong electric fields has been studied in quasi-one-dimensional (Q1D) organic conductors. Numerical and experimental results on the electric field effect are presented. For each sheet-like Fermi surface, the interlayer electric field works as the effective magnetic field giving the same force, so that the phenomena depending on magnetic field orientations must show shift generally. We show that the Lebed resonances, the most basic angular effect in the Q1D system, show shift (or split) under electric fields, and demonstrate that the Fermi velocity can be estimated from these experiments. By combining the electric field effect, the magnetoresistance angular effects could be the more useful tool to study not only the Fermi surface topology but also the band dispersion in Q1D conductors. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0379-6779(02)00278-3

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  • Electric field effect on magnetoresistance angular effects in low-dimensional organic conductors Reviewed

    Synthetic Metals   2003.3

  • Electric field effect on magnetoresistance angular effects: new tool to study mass renormalization in quasi-one-dimensional organic conductors Reviewed

    K Kobayashi, E Ohmichi, T Osada

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   63 ( 6-8 )   1267 - 1271   2002.6

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    We discuss a novel experimental method to study mass renormalization in quasi-one-dimensional (Q I D) conductors having open sheet-like Fermi surfaces. It is well known that the detailed shape of the sheet-like Fermi surface could be studied by using magetoresistance angular effects, which appear on the interlayer magnetoresistance as a function of magnetic field orientations. We have taken notice of the effect of additional electric fields on the magnetoresistance angular effects. The basic concept is as the followings. In the Q1D system, the interlayer electric field can be replaced with the effective magnetic field, which gives the same Lorentz force to an electron, for each Fermi sheet. So, the angular effects due to different Fermi sheets must show different shifts under electric fields. From this shift, we can directly estimate the Fermi velocity and/or the electron mass in the Q1D conductors. We have numerically checked this electric field effect, and have also experimentally confirmed the electric field effect in organic conductors (TMTSF)(2)ClO4 and alpha-(BEDT-TTF)(2)KHg(SCN)(4), which have Q1D electron systems at low temperatures. (C) 2002 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0022-3697(02)00113-0

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  • Angular dependent magnetotransport and electronic structure in quasi-one-dimensional organic conductor (TMTSF)(2)ClO4 Reviewed

    K Kobayashi, T Osada

    SYNTHETIC METALS   120 ( 1-3 )   1029 - 1030   2001.3

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    Anisotropic magnetotransport in a quasi-one-dimensional (Q1D) organic conductor (TMTSF)(2)ClO4 are discussed relating to its electronic structure. (1) The Lebed resonance is semiclassically considered for general field orientations. The Danner-Chaikin oscillation is not an independent phenomenon, but it is regarded as the oscillation of Lebed resonance amplitude. (2) In (TMTSF)(2)ClO4, the Lebed resonance position reflects the anion ordering (AO) superlattice. Using this fact, the lower limit of AO gap is estimated. (3) The magnetoresistance angular effects under d.c. electric fields are numerically studied. The angular effect structures doubly split and shift under electric fields along the stacking axis. This effect can be explained by the fact that electrons on each Fermi sheet feel different effective magnetic fields.

    DOI: 10.1016/S0379-6779(00)01095-X

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  • Evidence for one-dimensional charge transport in the stripe ordered phase of La(2-x-y)Nd(y)Sr(x)CuO(4) Reviewed

    T Noda, K Kobayashi, H Eisaki, S Uchida

    ADVANCES IN SUPERCONDUCTIVITY XII   155 - 157   2000

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    Doping dependence of the Hall coefficient (R(H)) is presented for La(1.4-x)Nd(0.6)Sr(x)CuO(4) in the spin-charge stripe ordered phase. For x less than or equal to 1/8, a remarkable decrease in the magnitude of R(H) at low temperatures provides evidence for one-dimensional charge transport. For x&gt;1/8, the R(H) remains relatively large in the stripe ordered phase. The results indicate a crossover from one- to two-dimensional charge transport taking place at x=1/8. Zn-substitution for Cu recovers the large values of R(H), indicating that disorder caused by Zn-substitution in the stripe ordered phase is destructive of one-dimensional charge transport.

    DOI: 10.1007/978-4-431-66877-0_39

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Books

  • Superconductivity in carbides

    Kobayashi Kaya( Role: Joint author)

    Springer  2019.7 

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MISC

  • μSR study in lightly electron doped Sr2-xLaxIrO4

    堀金和正, 角田了, 岡部博孝, 町田一樹, 堀江理恵, 小林夏野, 小林夏野, 秋光正子, 幸田章宏, 門野良典, 秋光純

    日本物理学会講演概要集(CD-ROM)   75 ( 1 )   2020

  • 新規超伝導体開発に向けた光電子ホログラフィーによるSr2-xLaxIrO4の原子サイト解析

    堀江理恵, 角田了, 室隆桂之, 松下智裕, 深見駿, 松田博之, 堀金和正, 小林夏野, 小林夏野, 春山雄一, 大門寛, 秋光純

    日本物理学会講演概要集(CD-ROM)   74 ( 1 )   2019

  • 高圧合成法を用いたアルカリ金属を含む新規超伝導体の探索および物性評価

    竹内和也, 堀金和正, 堀江理恵, 小林夏野, 小林夏野, 磯部雅朗, 秋光純

    日本物理学会講演概要集(CD-ROM)   74 ( 1 )   2019

  • (Sr,La)2IrO4のSTM/STS測定

    幸坂祐生, 藤井政徳, 堀金和正, 小林夏野, 小林夏野, 堀江理恵, 花栗哲郎, 秋光純

    日本物理学会講演概要集(CD-ROM)   74 ( 1 )   2019

  • μSR法を用いたSr2-xLaxIrO4の磁気相図の決定

    町田一樹, 堀金和正, 藤井政徳, 岡部博孝, 小林夏野, 小林夏野, 堀江理恵, 石井啓文, 久保園芳博, 久保園芳博, 幸田章宏, 門野良典, 秋光純

    日本物理学会講演概要集(CD-ROM)   74 ( 1 )   2019

  • Angle-resolved photoemission study on (Sr,La)2IrO4

    TERASHIMA Kensei, SUNAGAWA Masonori, FUJIWARA Hirokazu, HORIGANE Kazumasa, FUJII Masanori, HORIE Rie, KOBAYASHI Kaya, AKIMITSU Jun, ONO Kanta, KUMIGASHIRA Hiroshi, MURAOKA Yuji, YOKOYA Takayoshi

    KEK Progress Report (Web)   ( 2018-7 )   2018

  • 層状Nb酸化物AB2Nb3O10の構造と超伝導

    川口貴弘, 堀金和正, 伊藤雄吾, 小林夏野, 小林夏野, 萩原雅人, LEE Shanghyun, 鳥居周輝, 神戸高志, 秋光純

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   2018

  • EXAFSによるキャリアドープSr2IrO4の局所結晶構造解析

    寺嶋健成, SALAS E., SIMONELLI L., PARIS E., JOSEPH B., 脇田高徳, 藤井政徳, 堀金和正, 小林夏野, 小林夏野, 堀江理恵, 秋光純, 村岡祐治, 村岡祐治, SAINI N. L., 横谷尚睦, 横谷尚睦

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   2018

  • メカニカルアロイ法によるSr2-xLaxIrO4の磁気相図

    堀金和正, 藤井政徳, 岡部博孝, 小林夏野, 堀江理恵, 石井啓文, LIAO Y-F., 久保園芳博, 幸田章宏, 門野良典, 秋光純

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   2018

  • SrIr2の超伝導

    堀江理恵, 西山佐希, 秋光正子, 堀金和正, 小林夏野, 小林夏野, 久保園芳博, 秋光純

    日本物理学会講演概要集(CD-ROM)   72 ( 1 )   2017

  • Growth and observation of micro-organic crystals in two-dimensional glass nanovolume cell

    Kaya Kobayashi, Hiroko Koyama, Kodai Ishikura, Toshiyuki Mitsui

    APPLIED PHYSICS LETTERS   93 ( 14 )   143114   2008.10

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    A simple type of glass cell to control the organic crystal growth in microsize by electrochemical method is presented. We fabricated growth cells with electrodes patterned by photolithograph and nanoliter volume. They have several merits for growth of organic conductors in microsize, including confined growth volume, observable growth space, rapid growth cycle relative to conventional methods, and compatibility with existing microfabrication techniques. The real time observation of the crystal growth was performed. The results are discussed in terms of the growth mechanism, suggesting a possibility of another microscopic view of crystal growth. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2999583]

    DOI: 10.1063/1.2999583

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  • Growth and observation of micro-organic crystals in two-dimensional glass nanovolume cell

    Kaya Kobayashi, Hiroko Koyama, Kodai Ishikura, Toshiyuki Mitsui

    APPLIED PHYSICS LETTERS   93 ( 14 )   143114   2008.10

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    Language:English   Publisher:AMER INST PHYSICS  

    A simple type of glass cell to control the organic crystal growth in microsize by electrochemical method is presented. We fabricated growth cells with electrodes patterned by photolithograph and nanoliter volume. They have several merits for growth of organic conductors in microsize, including confined growth volume, observable growth space, rapid growth cycle relative to conventional methods, and compatibility with existing microfabrication techniques. The real time observation of the crystal growth was performed. The results are discussed in terms of the growth mechanism, suggesting a possibility of another microscopic view of crystal growth. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2999583]

    DOI: 10.1063/1.2999583

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  • 層状低次元導体における磁気抵抗角度効果(Ⅱ) -高電場下の層間磁気伝導- Invited

    長田俊人, 蔵口雅彦, 小早川将子, 小林夏野, 池田悟, 大道英二

    固体物理   42 ( 3 )   157 - 167   2007.3

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  • Electric-field effect on the angle-dependent magnetotransport properties of quasi-one-dimensional conductors

    K Kobayashi, M Saito, E Ohmichi, T Osada

    PHYSICAL REVIEW LETTERS   96 ( 12 )   126601-1-126601-4   2006.3

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    Language:English   Publisher:AMERICAN PHYSICAL SOC  

    We report a novel electric field effect on angular dependent magnetotransport in quasi-one-dimensional layered conductors with a pair of sheetlike Fermi surfaces. Under tilted magnetic fields and additional interlayer electric fields, semiclassical electron orbits on two Fermi sheets become periodic at different magnetic field orientations. This causes double splitting of the Lebed's commensurability resonance in interlayer transport, and the amount of splitting allows us to estimate the Fermi velocity directly. We have successfully demonstrated this effect in the organic conductor alpha-(BEDT-TTF)(2)KHg(SCN)(4).

    DOI: 10.1103/PhysRevLett.96.126601

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  • Angular-Dependence of the Magnetoresistance in a Low-dimensional Conductor under High Electric Field

    Kobayashi K., Ohmichi E., Osada T.

    Meeting abstracts of the Physical Society of Japan   57 ( 2 )   715 - 715   2002.8

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

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Presentations

  • Possible valence skipping superconductivity in doped Dirac metal Invited

    Kaya Kobayashi, T. Ueno, T. Wakita, T. Furukawa, T. Itou, T. Yokoya

    Material Research Meeting 2019  2019.12.13 

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    Event date: 2019.12.10 - 2019.12.14

    Language:English   Presentation type:Oral presentation (invited, special)  

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  • 量子極限近傍における角度依存磁気抵抗振動の量子効果

    日本物理学会第59回年次大会(日本物理学会)  2004 

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  • Quantum Features of Angular Dependent Magnetoresistance Oscillations in Q2D Conductors near High Magnetic Field Quantum Limet

    ICSM(ICSM2004)  2004 

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  • Study of Electronic Structure of Low Temperature Phase in K-(BEDーTTF)_2 KHg(SCN)_4 Using Angular Dependent Magnetoresistance Oscillations

    ISCOM(ISCOM2003)  2003 

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  • 擬1次元導体の磁気抵抗効果における量子効果

    日本物理学会第58回年次大会(日本物理学会)  2003 

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  • Electric Field Effect on Vertical Transport in Multilayer Systems under Tilted Magnetic Fields

    EP2DS(EP2DS15)  2003 

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  • Growth and Transport Measurement of (TMTSF)_2PF_6/(TMTSF)_2ClO_4

    ICSM(ICSM2002)  2002 

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  • 低次元導体の磁気抵抗角度効果の強電場効果

    日本物理学会秋季大会(日本物理学会)  2002 

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Works

  • 微小電極を用いた微小低次元有機導体伝導測定法の確立(単独)

    2007.4
    -
    2008.3

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  • “Electric Field Effect on Vertical Magnetotransport in Multilays Systems under Tilted Magnetic Field”(Physica E(Elsevier))

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  • “Growth and Transport Measurement of (TMTSF)_2PF_6/(TMTSF)_2 ClO_4 Hetero-Junctions”(Synthetic Metals(Elsevier))

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Awards

Research Projects

  • Morphology control of PBA core-shell nanoparticles and the TEM observation of Nano-hetero surfaces

    Grant number:20K05272  2020.04 - 2023.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    糸井 充穂, 小松 徳太郎, 小林 夏野

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    Authorship:Coinvestigator(s) 

    Grant amount:\3120000 ( Direct expense: \2400000 、 Indirect expense:\720000 )

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  • 新たな電気磁気交差現象 ― 電流誘起磁性 ― の学理の構築

    Grant number:19H01852  2019.04 - 2022.03

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    伊藤 哲明, 小林 夏野

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    Grant amount:\17940000 ( Direct expense: \13800000 、 Indirect expense:\4140000 )

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  • Valence-skip mechanism of superconductivity in doped Dirac electron system

    Grant number:18K03540  2018.04 - 2021.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    小林 夏野

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    Grant amount:\4420000 ( Direct expense: \3400000 、 Indirect expense:\1020000 )

    高温超伝導発現機構として提唱されたバレンススキップ超伝導機構は、その候補物質は少なく提唱されてから30年ほどたつにもかかわらずいくつかの例を除き研究が進んでいない。本研究で対象とするAgSnSe2は非常に単純な構造を持つ超伝導転移温度Tc~5 Kの超伝導体であり、その格子定数とTcが比例関係を持つこと知られていた。この超伝導発現にはSnの価数が2+と4+の2種類が存在する必要があることがXPS測定から明らかになったことから、バレンススキップ超伝導候補物質として期待できる。AgSnSe2は同時に、NaCl型SnSeのSnサイトにAgを置換した系としてみなすこともできる。仮想物質であるNaCl型SnSeはディラックコーンを持つ半導体であると考えられる。このようなSnSeにドープしたAgSnSe2は、有力なトポロジカル超伝導体候補であるInドープSnTeと同様の状態になっていることが期待される。
    以上の期待から良質の単結晶合成を行い、トポロジカル性やバレンススキップ超伝導の機構解明を目指す。具体的には組成を制御し不純物を除いた単結晶試料を合成し、トポロジカル性の検証に有効な角度分解光電子分光や価数の変化がわかる分光測定を行ってトポロジカル性と超伝導発現機構の両面から電子状態を明らかにする。
    初年度においては多結晶試料を中心に合成を行い、合成時における不純物によって大きく電子状態が左右されうること、またその制御が試料の室に大きく影響を与えることを明らかにした。また良質多結晶試料を用いた単結晶合成によって、単結晶試料の合成に成功した。

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  • New magnetoelectric effect and nuclear spin manupulation in elemental tellurium

    Grant number:15K13524  2015.04 - 2017.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research  Grant-in-Aid for Challenging Exploratory Research

    Itou Tetsuaki

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    Grant amount:\3770000 ( Direct expense: \2900000 、 Indirect expense:\870000 )

    The magnetoelectric effect (electric/magnetic stimulus generates magnetic/electric response) in bulk matter is of growing interest both fundamentally and technologically. This effect has been studied intensively in multiferroic materials. We have discovered a new class of bulk magnetoelectric phenomenon, which is fundamentally distinct from that in multiferroic materials. We have demonstrated experimentally that in elemental tellurium, bulk magnetization is induced parallel to an applied current, which is quite beyond classical electromagnetism and the current framework for magnetoelectricity in multiferroic materials.

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Class subject in charge

  • Solid State Physics 2 (2021academic year) 1st and 2nd semester  - 木1,木2

  • Solid State Physics 2A (2021academic year) 1st semester  - 木1,木2

  • Solid State Physics 2B (2021academic year) Second semester  - 木1,木2

  • Solid State Physics 3 (2021academic year) 1st semester  - 木1,木2

  • Solid State Physics 4 (2021academic year) Second semester  - 木1,木2

  • Introduction to Interdisciplinary Science 2 (2021academic year) Prophase  - 水1,水2

  • Introduction to Physical Science (2021academic year) 3rd and 4th semester  - 火3,火4

  • Introduction to Physical Science A (2021academic year) Third semester  - 火3,火4

  • Introduction to Physical Science B (2021academic year) Fourth semester  - 火3,火4

  • Seminar in Physics of Solid Surfaces and Interfaces (2021academic year) Year-round  - その他

  • Introduction to Natural Science 1(Physics) (2021academic year) 1st semester  - 火3~4

  • Introduction to Natural Science 2(Physics) (2021academic year) Second semester  - 火3~4

  • Quantum Magnetism of Matter (2021academic year) Late  - 木3,木4

  • Physics of quantum electronics (2021academic year) Late  - その他

  • Solid State Physics 2 (2020academic year) 1st and 2nd semester  - 木1,木2

  • Solid State Physics 3 (2020academic year) 1st semester  - 木1,木2

  • Solid State Physics 4 (2020academic year) Second semester  - 木1,木2

  • Introduction to Interdisciplinary Science 1 (2020academic year) Prophase  - 水1,水2

  • Solid-state Synchrotron Spectroscopy (2020academic year) Prophase  - 火1,火2

  • Seminar in Physics of Solid Surfaces and Interfaces (2020academic year) Year-round  - その他

  • Physics of quantum electronics (2020academic year) Late  - その他

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Media Coverage

  • 東京理科大学、岡山大学 テルル、電流で磁化 次世代情報処理技術に Newspaper, magazine

    化学工業日報  2017.10.24

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    Author:Other 

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