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Kohama Group

member
Associate Professor KOHAMA,Yoshimitsu
Research Associate NOMURA, Toshihiro

Research Subjects

  • Magneto-optical measurements with laser optics and its application to ultra-high magnetic field science
  • NMR measurement under pulsed fields and its application to magnetic materials
  • Development of new measurement techniques with nanofabrication technology
  • Observation of quantum oscillation in ultra-high magnetic fields and fermiology of topological insulators

Ultra-high magnetic field (higher than 100 T) is an extreme condition that remains unexplored until recently. In this field region, many of unprecedented phenomena are expected to appear, and their experimental observations and understandings are the focus of our group. To achieve this goal, we employ/develop the following experimental techniques, “1. Magneto-optical measurement under pulsed magnetic fields”, “2. Ultra-fast magnetoresistance measurement with micro-fabricated devices”, “3. Pulsed-field NMR experiment with a FPGA module”, and “4. Time-resolved neutron diffraction under long pulsed fields”, and so on. With these state-of-the-art techniques, we currently investigate various field-induced phenomena, such as the quantum transport in topological insulators/superconductors and the novel magnetic phases in quantum spin systems. Our final goal is the extension of the available field range of a condensed matter research up to ~1000 T, and thus our efforts are also devoted to technical developments for ultra-high magnetic field generations as well as the further improvements of measurement techniques.

(a) Magnetic-field-versus-temperature (H-T) phase diagram of CuInCr4S8. (b) Predicted schematic of the magnetic structures for X-, Y-, and C phases. (c) Adiabatic magnetocaloric effect curves (gray) near the A-phase where abnormal magnetostriction and magnetocapacitance responses are observed.
Relative changes of the sound velocity of (a) green dioptase and (b) liquid oxygen measured by using the single-turn coil megagauss generator.

Publications and Research Highlights