Wataru KOBAYASHI

Affiliation:      Division of Physics, Faculty of pure and applied sciences,
University of Tsukuba, Assistant professor
Address:Tennodai 1-1-1, Tsukuba-city, Ibaraki 305-8571
Tel&Fax:+81-2-9853-4276
E-mail:kobayashi.wataru.gf_at_u.tsukuba.ac.jp
ID: Google Scholar
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ORCiD
in japanese: Researchers Information

CV

Apr.1997 - Mar.2001      Department of Physics, School of Science and Engineering, Waseda University, B.S.
Apr.2001 - Aug.2002Graduate School of Pure and Applied Physics, Waseda University, M.S.
Sep.2002 - Oct.2005Graduate School of Pure and Applied Physics, Waseda University, Ph.D
Thesis: “High-temperature quantum phenomena of A-site ordered transition-metal oxides
in strongly correlated electron system” (in Japanese), Supervisor: Professor Ichiro Terasaki
Apr.2003 - Mar.2006JSPS Research Fellowship for Young Scientists DC1->PD
Apr.2006 - Sep.2006Visiting lecturer, Waseda University
Oct.2006 - Dec.2007Postdoctoral researcher, CRISMAT laboratory, France
Dec.2007 - Aug.2010Assistant Professor, Waseda Institute for Advanced Study, Waseda University
Sep.2010 - currentAssistant Professor, Division of Physics, Faculty of pure and applied sciences, University of Tsukuba

Research field

condensed matter physics, transport

Awards

Jan.2017       Young faculty member award, University of Tsukuba
Feb.2011JPSJ Papers of Editors' choice award (co-author)
Dec.2008IUMRS-ICA2008 Young Researcher Award
Aug.2006Presentation award, thermoelectric society of Japan

Member

Apr.2021 - Mar.2025     class teacher
Dec.2008 - current     facilitator of society for new magnetic materials
Jul.2012 - currentcouncilor of The Thermoelectrics Society of Japan

Lectures (2024)

Advanced course for strongly correlated system IA
Advanced course for strongly correlated system IB
Experiments II (X-ray diffraction)

Lectures (2023)

Problem-seeking seminar
Experiments II (X-ray diffraction)

Lectures (2022)

Problem-seeking seminar
Advanced course for strongly correlated system IA
Advanced course for strongly correlated system IB
Experiments II (X-ray diffraction)

Notice for (foreign) students

I'm sorry, but currently I don't accept any (foreign) student.

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Selected papers

  1. W. Kobayashi,
    "Analytical expression of negative differential thermal resistance in a macroscopic heterojunction"
    J. Stat. Mech., 023204 (2024).
    doi.org/10.1088/1742-5468/ad1beb
    arXiv:2302.14065

  2. W. Kobayashi,
    "Thermopower in transition-metal perovskites"
    Phys. Rev. B 104, 245108 (2021).
    doi.org/10.1103/PhysRevB.104.245108
    arXiv:2109.07769

  3. W. Kobayashi,
    "Thermal-rectification coefficients in solid-state thermal rectifiers"
    Phys. Rev. E 102, 032142 (2020).
    doi.org/10.1103/PhysRevE.102.032142

  4. W. Kobayashi, A. Yanagita, T. Akaba, T. Shimono, D. Tanabe, and Y. Moritomo,
    "Thermal Expansion in Layered NaxMO2"
    Sci. Rep. 8, 3988 (2018).
    doi.org/10.1038/s41598-018-22279-9

  5. T. Shibata, Y. Fukuzumi, W. Kobayashi, and Y. Moritomo,
    "Thermal power generation during heat cycle near room temperature"
    Appl. Phys. Exp. 11, 017101 (2018).
    doi.org/10.7567/APEX.11.017101

  6. S. Akama, W. Kobayashi, K. Amaha, H. Niwa, H. Nitani, and Y. Moritomo,
    "Local structures around the substituted elements in mixed layered oxides"
    Sci. Rep. 7, 43791 (2017).
    doi.org/10.1038/srep43791

  7. K. Amaha, W. Kobayashi, S. Akama, K. Mitsuishi, and Y. Moritomo,
    "Interrelation between inhomogeneity and cyclability in O3-NaFe1/2Co1/2O2"
    Physica Status Solidi (RRL) 11, 1600284 (2017).
    doi.org/10.1002/pssr.201600284

  8. W. Kobayashi, A. Kinoshita, and Y. Moritomo,
    "Seebeck effect in a battery-type thermocell"
    Appl. Phys. Lett. 107, 073906 (2015).
    doi.org/10.1063/1.4928336

  9. T. Shibata, Y. Fukuzumi, W. Kobayashi, and Y. Moritomo,
    "Fast discharge process of layered cobalt oxides due to high Na+ diffusion"
    Sci. Rep. 5, 9006 (2015).
    doi.org/10.1038/srep09006

  10. W. Kobayashi and Y. Moritomo,
    "Ionic model approach to battery voltage of NaMO2"
    J. Phys. Soc. Jpn. 83, 104712 (2014).
    doi.org/10.7566/JPSJ.83.104712

  11. T. Shibata, W. Kobayashi, and Y. Moritomo,
    "Sodium ion diffusion in layered NaxMnO2 (0.49 ≤ x ≤ 0.75): Comparison with NaxCoO2"
    Appl. Phys. Express 7, 067101 (2014).
    doi.org/10.7567/APEX.7.067101

  12. T. Shibata, W. Kobayashi, and Y. Moritomo,
    "Intrinsic rapid Na+ intercalation observed in NaxCoO2 thin film"
    AIP Advances 3, 032104 (2013).
    doi.org/10.1063/1.4794719

  13. W. Kobayashi, D. Sawaki, T. Omura, T. Katsufuji, Y. Moritomo, and I. Terasaki,
    "Thermal rectification in the vicinity of a structural phase transition"
    Appl. Phys. Express 5, 027302 (2012).
    doi.org/10.1143/APEX.5.027302

  14. W. Kobayashi, Y. Koizumi, and Y. Moritomo,
    "Large thermal Hall coefficient in bismuth"
    Appl. Phys. Lett. 100, 011903 (2012).
    doi.org/10.1063/1.3673562

  15. W. Kobayashi, Y. Hayashi, M. Matsushita, H. Yamamoto, I. Terasaki, A. Nakao, H. Nakao, T. Murakami, Y. Moritomo, H. Yamauchi, and M. Karppinen,
    "Anisotropic thermoelectric properties of quasi-one-dimensional SrNbO3.4+d (d~ 0.03)"
    Phys. Rev. B 84, 085118 (2011).
    doi.org/10.1103/PhysRevB.84.085118

  16. D. Sawaki, W. Kobayashi, Y. Moritomo, and I. Terasaki,
    "Thermal rectification in bulk materials with asymmetric shape"
    Appl. Phys. Lett. 98, 081915 (2011).
    doi.org/10.1063/1.3559615

  17. W. Kobayashi,
    "Transport properties of quasi-one-dimensional KRu4O8"
    Phys. Rev. B 79, 085207 (2009).
    doi.org/10.1103/PhysRevB.79.155116

  18. W. Kobayashi, Y. Teraoka, and I. Terasaki,
    "An oxide thermal rectifier"
    Appl. Phys. Lett. 95, 171905 (2009).
    doi.org/10.1063/1.3253712

  19. W. Kobayashi, S. Hebert, O. Perez, D. Pelloquin, and A. Maignan,
    "Metallicity in crystals of the quasi 1D rhodate Ba1.2Rh8O16"
    Phys. Rev. B 79, 085207 (2009).
    doi.org/10.1103/PhysRevB.79.085207

  20. W. Kobayashi, W. Tamura, and I. Terasaki,
    "Thermal conductivity of thermoelectric rhodium oxides measured by a modified Harman method"
    J. Phys. Soc. Jpn. 77, 074606 (2008).
    doi.org/10.1143/JPSJ.77.074606

  21. W. Kobayashi, S. Hebert, D. Pelloquin, O. Perez, and A. Maignan,
    "Enhanced thermoelectric properties in a two-dimensional rhodium oxide with a trigonal symmetry"
    Phys. Rev. B 76, 245102 (2007).
    doi.org//10.1103/PhysRevB.76.245102

  22. W. Kobayashi, S. Ishiwata, I. Terasaki, M. Takano, I. Grigoraviciute, H. Yamauchi, and M. Karppinen,
    "Room-temperature ferromagnetism in Sr1-xYxCoO3-d (0.2 <= x <= 0.25)"
    Phys. Rev. B 72, 104408 (2005).
    doi.org/10.1103/PhysRevB.72.104408

  23. W. Kobayashi and I. Terasaki,
    "CaCu3Ti4O12/CaTiO3 composite dielectrics: Ba/Pb-free dielectric ceramics with high dielectric constants"
    Appl. Phys. Lett. 87, 032902 (2005).
    doi.org/10.1063/1.1997278

  24. W. Kobayashi, I. Terasaki, J. Takeya, I. Tsukada, and Yoichi Ando,
    "A novel heavy fermion state in CaCu3Ru4O12"
    J. Phys. Soc. Jpn. 73, 2373 (2004).
    doi.org/10.1143/JPSJ.73.2373

  25. W. Kobayashi, I. Terasaki, M. Mikami, R. Funahashi, T. Nomura and T. Katsufuji,
    "Universal charge transport of the Mn oxides in the high temperature limit"
    J. Appl. Phys. 95, 6825 (2004).
    doi.org/10.1063/1.1687532

  26. W. Kobayashi, A. Satake, and I. Terasaki,
    "Thermoelectric Properties of the Brownmillerite Oxide Ca2-yLayCo2-xAlxO5 "
    Jpn. J. Appl. Phys. 41, 3025 (2002).
    doi.org/10.1143/JJAP.41.3025

Research interests

fundamental research

  • Quantum many body system (unconventional superconductivity, non-Fermi liquid, spin crossover, quantum information)
  • Non-equilibrium thermodynamics (from quantum to classical)
  • Calculation of phenomenological coefficients based on quantum statistical mechanics

    • application

  • Cross correlation in between fluxes and control of the fluxes
  • Transport phenomena in thermocell (ion, redox)
  • Themoelectric transport in thermoelectrics (charge, spin, orbital)
  • Thermal control under magnetic field in semimetals with high mobility (relativistic)
  • Thermal transport in thermal diode
  • Chemical potential and ionic transport in secondary-battery

    • Research content (2002-->current)

    fundamental point of view (2003-->2012)

  • heavy fermion --> spin crossover --> non-Fermi liquid --> relativistic

    • applicational point of view (2002-->current)

  • thermoelectrics --> thermal diode --> thermal Hall (2002-->2012)

    • 3d: perovskite Co, Mn, Ti, layered Co oxides
    4d: quasi 1D Nb, perovskite Ru, layered Rh, quasi 1D Rh oxides
    5d: quasi 1D Ir oxide
    6s: Bi

  • others [dielectrics, spin Seebeck effect (joint-research)] (2002-2005, 2012)
  • Na-ion battery (thin film, voltage, diffusion coefficient, (local) structure, cyclability) --> thermocell (thermogalvanic) (2013-->current)

    • 3d: P2-NaxMO2, O3-NaMO2, Prussian-Blue analogues with Fe(CN)6

    theoretical point of view (2014-->current)

  • battery voltage --> thermal expansion --> thermal rectification --> thermopower --> negative differential thermal resistance

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