Sugimoto, Koudai

写真a

Affiliation

Faculty of Science and Technology, Department of Physics （Yagami）

Position

Senior Assistant Professor (Non-tenured)/Assistant Professor (Non-tenured)
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Papers 【 Display / hide 】

  • Successive magnetic transitions in the heavy-fermion superconductor Ce3PtIn11 studied by in 115 nuclear quadrupole resonance

    Fukazawa H., Kumeda K., Shioda N., Lee Y., Kohori Y., Sugimoto K., Das D., Bławat J., Kaczorowski D.

    Physical Review B （Physical Review B)  102 （ 16 ）  2020.10

    ISSN  24699950

    　View Summary

    © 2020 American Physical Society. Nuclear quadrupole resonance (NQR) measurements were performed on the heavy-fermion superconductor Ce3PtIn11 with Tc=0.32K. The temperature dependence of both spin-lattice relaxation rate 1/T1 and NQR spectra evidences the occurrence of two successive magnetic transitions with TN1≃2.2K and TN2≃2.0K. In successive magnetic transitions, even though the magnetic moment at the Ce(2) site plays a major role, the magnetic moment at the Ce(1) site also contributes to some extent. While a commensurate antiferromagnetic ordered state appears for TN2<T<TN1, a partially incommensurate antiferromagnetic ordered state is suggested for T<TN2.

  • Successive magnetic transitions in the heavy-fermion superconductor Ce3PtIn11 studied by 115In nuclear quadrupole resonance

    Hideto Fukazawa, Kazuki Kumeda, Naoki Shioda, Yongsun Lee, Yoh Kohori, Koudai Sugimoto, Debarchan Das, Joanna Bławat, Dariusz Kaczorowski

    Physical Review B 102   165124 2020.10

    Research paper (scientific journal), Joint Work, Accepted

  • Superconductivity and charge density wave under a time-dependent periodic field in the one-dimensional attractive Hubbard model

    Fujiuchi R., Kaneko T., Sugimoto K., Yunoki S., Ohta Y.

    Physical Review B （Physical Review B)  101 （ 23 ） 235122 2020.06

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  24699950

    　View Summary

    © 2020 American Physical Society. We investigate the competition between superconductivity (SC) and charge density wave (CDW) under a time-dependent periodic field in the attractive Hubbard model. By employing the time-dependent exact diagonalization method, we show that the driving frequency and amplitude of the external field can control the enhancement of either the superconducting pair or the CDW correlation in the system, for which SC and CDW are degenerate in the ground state of the half-filled attractive Hubbard model in the absence of the field. In the strong-coupling limit of the attractive Hubbard interaction, the controllability is characterized by the anisotropic interaction of the effective model. The anisotropy is induced by the external field and lifts the degeneracy of SC and CDW. We find that the enhancement or suppression of the superconducting pair and CDW correlations in the periodically driven attractive Hubbard model can be well interpreted by the quench dynamics of the effective model derived in the strong-coupling limit.

  • Finite-Temperature Properties of Excitonic Condensation in the Extended Falicov–Kimball Model: Cluster Mean-Field-Theory Approach

    Masahiro Kadosawa, Satoshi Nishimoto, Koudai Sugimoto, Yukinori Ohta

    Journal of the Physical Society of Japan （Journal of the Physical Society of Japan)  89 （ 5 ） 053706-1 - 053706-5 2020.05

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  00319015

    　View Summary

    ©2020 The Physical Society of Japan We study the electron–hole pair (or excitonic) condensation in the extended Falicov–Kimball model at finite temperatures based on the cluster mean-field-theory approach, where we make the grand canonical exact-diagonalization analysis of small clusters using the sine-square deformation function. We thus calculate the ground-state and finite-temperature phase diagrams of the model, as well as its optical conductivity and single-particle spectra, thereby clarifying how the preformed pair states appear in the strong-coupling regime of excitonic insulators. We compare our results with experiments on Ta2NiSe5,.

  • Observation of a Novel Phase Transition in Sr7Re4O19

    Yutaka Ueda, Mina Murase, Yoshiaki Kobayashi, Masayuki Itoh, Takeshi Yajima, Tomoki Yamaguchi, Ryo Takahashi, Koudai Sugimoto, Yukinori Ohta

    Journal of the Physical Society of Japan （Journal of the Physical Society of Japan)  89 （ 5 ） 054703-1 - 054703-5 2020.05

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  00319015

    　View Summary

    © 2020 The Physical Society of Japan. We have synthesized good-quality powder samples of Sr7Re4O19 and found a phase transition at 206 K accompanied by some changes in both electronic properties and structure. The values and the temperature dependence of magnetic susceptibility indicate the existence of a Pauli paramagnetic state above 206 K and a nonmagnetic state below 206 K. The electrical resistivity of the sintered sample gradually increases with decreasing temperature below room temperature and sharply increases below 206 K, which is followed by insulating behavior below 160 K. In addition, the structure changes from monoclinic to triclinic at the transition. Sr7Re4O19 has a quasi-one-dimensional structure comprising the coupled zigzag chain formed by corner-shared ReO6 octahedra. Further, a long=short alternation of the Re–Re distance along the zigzag chain is observed in the low-temperature phase. Quasi-one-dimensional Fermi surfaces and band dispersions are also identified by the electronic structure calculations. These results suggest that the phase transition is a possible metal–insulator transition caused by the Peierls instability.

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Papers, etc., Registered in KOARA 【 Display / hide 】

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

  • Ultrafast spectroscopy simulation of low-dimensional strongly correlated electron systems using tensor network

    2023.04
    -
    2027.03

    基盤研究(C), Principal investigator

  • Excitation dynamics in excitonic condensation phase

    2019.04
    -
    2022.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Early-Career Scientists , Principal investigator

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Courses Taught 【 Display / hide 】

  • PHYSICS EXERCISE 3

    2024

  • PHYSICS D

    2024

  • PHYSICS C

    2024

  • LITERATURE OF PHYSICS

    2024

  • BACHELOR'S THESIS

    2024

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