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Katsumoto Group

Research Associate

Research Associate

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With epitaxial growth of semiconductor and metallic films, and nano-fabrication techniques, we study quantum effects in low dimensional systems. Our research also spans some applications of the physics of electron and nuclear spins to so called spintronics. To expand the concept of quantum transport to spin degree of freedom, we have tried to create spin currents in quantum structures with (1) combination of the spin-orbit interaction (SOI) and nano-structures, also with (2) spin-injection in semiconductor/ferromagnet monolithic structure. In two-dimensional electrons with a strong SOI, we have realized spin interference devices and also found phenomenon called “Zitterbewegung” (trembling motion). Spin injection from epitaxially grown Fe films with a high efficiency has been achieved. In a hybrid system of superconductor and a diluted ferromagnetic semiconductor we have observed superconducting Josephson currents.

Fourier power spectra of conductance fluctuation against in-plane magnetic field due to “Zitterbewegung” (trembling motion) of electrons in InAs two-dimensional electrons. The parameter is the azimuth angle φ of the field as defined in the scanning electron micrograph of the sample in the inset, in which the red arrow indicates the electron path.
Magnetization curve of a diluted magnetic semiconductor (In,Fe)As, which is used as an insulation layer of a Josephson junction. The upper-left inset shows the differential resistance as a function of the voltage, in which IC indicates the critical current. The lower-right inset shows the critical current as a function of magnetic field. Very rapid oscillation of IC against the field is recognizable.

Research Subjects

  1. Quantum transport in charge and spin freedoms
  2. Study of many-body effects in quantum structures
  3. Physics at interfaces between the phases with different symmetries