Home >  Research > International MegaGauss Science Laboratory > Kohama Group

Kohama Group

Associate Professor KOHAMA,Yoshimitsu

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.

Unique magnetic field response of α-(BETS)2I3 (a) Magnetoresistance at low temperatures. When a magnetic field is applied parallel to the current, a negative magnetoresistance due to the chiral magnetic effect is observed. (b) Positive magnetoresistance is observed when a magnetic field is applied perpendicular to the current.
Long pulsed magnetic field generated by coil using high-purity copper (6N) wire. The black line is a pulsed magnetic field generated by a high-purity copper coil cooled with liquid helium. The red line is a pulsed magnetic field generated by a high-purity copper coil cooled with liquid nitrogen.

Publications and Research Highlights