Graduate School of Engineering
Department of Materials Science

Nano-materials Science
Materials Quantum Science (Prof. Nitta)

Research Topics

Semiconductor Spintronics

Semiconductor and ferromagnetic materials are indispensable for present electronics technologies. Ferromagnetic metals show a magnetization hysteresis loop in which the cooperative motion of large number of electron spins plays a role. In semiconductor electronics, electron charge plays the key role while electron spin plays no role at all. Electronics based on the spin degrees of freedom of the electron represents a new paradigm, which will require a way of controlling electron spins in semiconductor channels by using the gate voltage.

We have experimentally confirmed that the spin-orbit interaction in a semiconductor two-dimensional electron gas channel can be controlled by gate electric fields. The key ingredient is the spin-orbit interaction which acts as the effective magnetic field for moving electrons. I order to manipulate spin states by electric field, we have demonstrated the gate control of the spin-orbit induced effective magnetic field, electrical spin generation by using InGaAs-based quantum point contact, spin geometric phase induced in mesoscopic ring structures, and nano-second spin dynamics probed by Time-resolve Kerr rotation spectroscopy. In addition to that, we also focus on the metal spintronics, where the magnetization reversal by spin-orbit induced effective magnetic fields, so called spin-orbit torque. We employ spin transfer ferromagnetic resonance to quantitatively evaluate the spin-orbit torque efficiency in Co/Pt and other ferromagnetic bilayer systems.

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