ISSP - The institute for Solid State Physics

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Osada Group
Associate Professor

Research Associate

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Transport study of low-dimensional electron system. To search for new phenomena in topological electron systems and electron systems confined by small spatial structures or strong magnetic fields, to clarify their mechanisms, and to control them for application. We have a great interest in quantum effects, topological effects, and many-body effects, which relate to Berry curvature of band structure, pseudo-spin degrees of freedom, and commensurability among electron orbital motions, vortex (magnetic flux) configuration, and spatial structures. Our targets are atomic layer materials such as graphene, low-dimensional materials such as organic conductors, and artificial semiconductor/superconductor nano-structures. We flexibly explore new transport phenomena and electronic states in small samples by electric, magnetic, and thermal measurements using fabrication techniques for building up atomic layer complexes (van derWaals heterostructures), nano-processing techniques like EB, precise field rotation, miniature pulse magnet, etc. under strong magnetic fields, high pressures, and low temperatures. Recently, we have concentrated our studies on quantum transport in atomic layer materials (graphene, phosphorene, etc.) and helical/chiral electron systems formed at the surface of topological phases.

Alignment and transfer device installed in a glovebox. This device can precisely align and fix an atomic layer on another atomic layer one by one, to build up atomic layer complexes (van der Waals heterostructures) in inert gas atmosphere. It is useful particularly for atomic layer materials unstable in the air.
Quantum Hall transport in monolayer/bilayer graphene junction. The sample was fabricated on the h-BN few atomic layer substrate, of which surface is flat and inactive, to develop the sample mobility. The behaviors of the longitudinal and Hall resistance across the junction indicate that only the topologically protected edge channels remain along junction. The fine structures around zero filling suggests the symmetry breaking of the ground Landau level.

Research Subjects

  1. Electronic structure and quantum transport in atomic layers (graphene, phosphorene, etc.)
  2. Helical surface state in quantum Hall ferromagnetic phase in an organic Dirac fermion system
  3. Quantum transport of chiral surface state in multilayer quantum Hall systems
  4. Interlayer coherence and angle-dependent magnetotransport in layered conductors
  5. Chaos and electron transport in Bloch electron systems under magnetic and electronic fields