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Kohama Group

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 those observations 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”. With these techniques, we currently investigate 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 future work will also be devoted to technical developments for ultra-high magnetic field generations as well as the further improvements of measurement techniques.

Zeeman splitting pattern of the R lines of Ruby. The non-linear Zeeman splitting was observed in ultra-high magnetic field region above 100 T. The inset shows the octahedrally coordinated Cr3+ ions in Al2O3 which is the cause of the photoluminescence of ruby.
Magnetoresistance of the upper critical field on Fe(Se,Te) superconductor. The upper critical field accompanied by the resistivity jump was observed around 40 T. The accessible field range for the magnetoresistance measurement is ~200 T.

Publications and Research Highlights