ISSP - The institute for Solid State Physics

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Osada Group
Associate Professor
OSADA,
Toshihito

Research Associate
TAEN,
Toshihiro

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Quantum transport in electron systems. We search for, elucidate, and control new electronic states and quantum transport phenomena that appear in topological materials, low-dimensional materials, and nanostructures. Targeting atomic layer materials such as graphene, their van der Waals complex stacks, topological insulators/semimetals, low-dimensional organic conductors, and artificial semiconductor/superconductor nanostructures, we investigate new topological or quantum effects in transport phenomena. Key experimental techniques are alignment and transfer for building up atomic layer stacks, micro-fabrication for small device structures, precise double-axis field rotation, miniature pulse magnet generating above 40T, etc. Recently, we have focused on studies on quantum transport in graphene junctions and black phosphorus thin-films, various topological phases in an organic conductor α-(BEDT-TTF)2I3, and the magnetic-field-induced electronic phase transition in graphite.

Gapped bulk band structure in an organic Dirac semimetal α-(BEDT-TTF)2I3 with finite spin-orbit interaction. Parities of wave functions are indicated at symmetric points. The parity product of -1 means that the system is a topological insulator. The inset shows the energy spectrum of finite system with the edge parallel to the one-dimensional chains. There appears a helical edge state in the gap.
Magnetoresistance of the black phosphorus thin-film FET device encapsulated by h-BN thin-films for several gate voltages. Single Shubnikov-de Haas oscillation of two-dimensional (2D) holes is observed in negative gate voltages. In contrast, double oscillations indicating the existence of two kinds of 2D electrons appear in positive high gate voltages. The inset shows an optical microscope image of the FET device.

Research Subjects

  1. Topological properties of an organic Dirac semimetal
  2. Electronic structure and quantum transport in atomic layers and their van der Waals stacks
  3. Quantum transport phenomena in layered topological materials
  4. Interlayer coherence and angle-dependent magnetotransport in layered conductors
  5. Magnetic-field-induced electronic phase transitions in thin-film graphite