Strongly Correlated Spin Research Team

Principal Investigator

PI Name Hazuki Furukawa
Degree Ph.D.
Title Team Leader
Brief Resume
1995Ph. D. in Physics, University of Tokyo
1995Special researcher on Basic Science, The Institute of Physical and Chemical Research (RIKEN)
1998Research Associate, Oak Ridge National Lab.
1999Associate Professor, Dep. of Physics, Faculty of Science, Ochanomizu Univ.
1999PRESTO, Japan Science and Technology Agency
2003Full Professor, Dep. of Physics, Faculty of Science, Ochanomizu Univ.
2007Full Professor, Division of Natural/Applied Science, Graduate School of Humanities and Sciences,
2015Full Professor, Faculty of Core Research Natural Science Division, Ochanomizu University (-present)
2016Team Leader, Strongly Correlated Spin Research Team, Strong Correlation Physics Division, RIKEN Center for Emergent Matter Science (-present)

Outline

Our team studies the static and dynamic magnetic and atomic structure of strongly correlated electron systems using various neutron scattering techniques. We are working to verify the relevance of physical characteristics in controlling and enhancing the behavior of these systems.
Research topics include; (1) Elucidation of the role of spin-orbit interactions in quantum states of newly discovered exotic superconductors, (2) Verification of FFLO phase and/or helical vortex phase, and (3) Study of the dynamics of skyrmions in topological magnetic materials.

Research Fields

Physics, Materials Science

Keywords

Strongly correlated electron system
Magnetism
Superconductivity
Skyrmion
Neutron scattering

Results

Contribution of phonon excitations to the superconducting mechanism of non-centrosymmetric LaNiC2

LaNiC2 is a superconductor (Tc = 2.7K) without spatial inversion symmetry. Theoretical group predicted that the phonon dispersion of this material may show kohn anomalies. In rare earth-nickel-boron-carbide superconductors (eg RENi2B2C), not only a kohn-anomaly but also resonance like peaks are observed at a specific q position, where nesting of the Fermi surface is expected to occur. To verify the possibility of both kohn-anomaly and resonance behaviors and to study their contribution to the mechanism of its superconductivity, we performed neutron scattering experiments. It was impossible to carry out a new experiment in FY 2020, we proceeded to analyze previous data measured by the high-resolution chopper spectroscope HRC in the J-PARC MLF of the Japan Atomic Energy Agency (JAEA). The results revealed longitudinal and transverse acoustic phonon branches. It was also clarified that a certain amount of phonon spectral was observed on the higher energy side but the intensity was too weak to identify the dispersion relation. We plan to conduct a new inelastic neutron scattering experiment in the experimental reactor JRR-3 at JAEA to draw the whole picture of the dispersion relation of the lattice fluctuation of this system.

Phonon excitation spectrum in a range of 7<E<9 meV at 300K and in the (H0L) scattering plane.

 

Superconducting mechanism and magnetic fluctuations in CeRh0.6Co0.4In5

CeCoIn5 has attracted much attention, since it shows several interesting phenomena, including a resonance magnetic peak, which appears below the superconducting transition temperature, Tc, a SDW magnetic order, a so-called “Q phase”, that is stabilized only in the superconducting phase. In this study, in order to clarify the relationship between magnetism and superconductivity, we performed inelastic neutron scattering experiments on CeRh0.6Co0.4In5. Resonance peaks accompanying the superconducting transition were not detected, but spin wave excitation appeared below TN along (1/2 1/2 l).

An analysis of the energy dependence of the excitation revealed that the dispersion relation in the [h h 0] direction is nearly independent of l. This suggests that there is a two-dimensional spin correlation in this system.

Energy dispersion curve of magnetic excitations observed along (1/2 1/2 l)

 

SANS experiment on beta−PdBi2 superconductor

For topological superconductors, special particles, so-called Majorana fermions, are predicted to appear on the surface of the material. We studied a candidate material of topological superconductors, β-PdBi2 (space group I4/mmm, Tc = 5.4 K), to bare its bulk properties including superconducting symmetry and gap structures by specific heat and small angle neutron scattering (SANS) measurements. For the present study, we succeeded in growing single crystals of β-PdBi2 by a melt growth method and Tc of the crystals was evaluated to be Tc = 5.2 K by magnetization measurements. Temperature dependence of neutron diffraction intensities originated from vortex lattice suggests that topological superconductor β-PdBi2 has an anisotropic superconducting full-gap. Moreover, we succeeded in revealing that the energy value of anisotropic full-gap estimated from small-angle neutron scattering experiments can reproduce the temperature dependence of electric heat capacity.

Temperature dependence of vortex Bragg diffraction of β-PdBi2.

Members

Hazuki Furukawa

Team Leader hazuki.furukawa[at]riken.jp R

Edward Thomas Foley

Technical Scientist

Publications

  1. M. Soda, S. Itoh, T. Yokoo, G. Ehlers, H. Kawano-Furukawa, and T. Masuda

    Magnetic correlations in YBaCo4O7 on kagome and triangular lattices

    Phys. Rev. B 101, 214444 (2020)
  2. M. Soda, T. Hong, M. Avdeev, H. Yoshizawa, T. Masuda, and H. Kawano-Furukawa

    Neutron scattering study of the quasi-one-dimensional antiferromagnet Ba2CoSi2O7

    Phys. Rev. B 100, 144410 (2019)
  3. A. Yokoyama, M. Soda, H. Yoshizawa, H. Kawano-Furukawa

    Memory Effect in Spin Glass Ni0.45Mn0.55TiO3

    JPS Conf. Proc. 30, 011185 (2019)
  4. M. Takahashi, H. Takeya, A. A. Aczel, T. Hong, M. Matsuda, and H. Kawano-Furukawa

    Neutron scattering study of spin density wave and weak ferromagnetic orders in (Tb0.47Y0.53Ni211B2C)

    Physica B 551, 108 (2018)
  5. M. Soda, L.-J. Chang, M. Matsumoto, V. O. Garlea, B. Roessli, J. S. White, H. Kawano-Furukawa, and T. Masuda

    Polarization analysis of magnetic excitation in multiferroic Ba2CoGe2O7

    Phys. Rev. B 97, 214437 (2018)

お問い合わせ

2-1 Hirosawa, Wako, Saitama 351-0198 Japan

TEL:+81-(0)48-467-9285

FAX:+81-(0)48-462-1687

E-mail:
hazuki.furukawa[at]riken.jp

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