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 Sciences

Keywords

Strongly correlated electron system
Magnetism
Superconductivity
Skyrmion
Neutron scattering

Results

Superconducting gap and mechanism of the 122 FeAs superconductor

Newly discovered FeAs superconductors are of much interest due to the relatively high maximum Tc. Among the family, KFe2As2 is a fully hole-doped end member, cf. (Ba, K)Fe2As2, with Tc ~ 3.6 K and we have tried to determine the symmetry of the superconducting gap by small angle neutron scattering technique, with a view to identifying the pairing mechanism. We succeeded in observing clear Bragg spots from the long range order of the vortex lattice (VL) (Phys. Rev. B 84, 024507 (2011)).  The VL with the magnetic field applied parallel to the c-axis shows no structural transitions up to 0.5Hc2, ruling out a strong basal plane anisotropy. However, the diffracted intensity at 0.1 T varied strongly with temperature down to 50 mK, indicating a range of gaps extending down to very low values. This is consistent with having multiple full superconducting gaps on different Fermi sheets or, alternatively, a nodal gap, but with the nodal lines horizontal, circulating around the approximately cylindrical sheets of the Fermi surface. After this study, we performed similar experiments on related material, BaFe2(As0.67P0.33)2, and succeeded in observing Bragg spots on this material, too. (Phys. Rev. B 90, 125116 (2014)).

SANS data for Bragg reflections from the vortex lattice in KFe2As2.

Members

Hazuki Furukawa

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

Minoru Soda

Research Scientist

お問い合わせ

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

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

Links

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