Sadao Takaoka

Magnetotransport in One-Dimensional Lateral Surface Superlattice Fabricated by Low-Energy Argon Ion Irradiation

One-dimensional lateral surface superlattice has been fabricated into the high-mobility heterostructure by low-energy ion irradiation and the magnetotransport properties are investigated. At weak magnetic field, Weiss oscillations are observed and this indicates that weak modulation potential is introduced in two-dimensional electron gas by low-energy ion irradiation. Moreover, Hall resistance oscillations are observed as theoretically predicted. A positive magnetoresistance observed around zero magnetic field is investigated in detail and is compared quantitatively with the theory of magnetic breakdown. At a high magnetic field where the cyclotron radius is much smaller than the superlattice period, anisotropic magnetoresistance with respect to the direction of current flow is observed.

Spin-Dependent Nonlocal Quantum Transport Influenced by Gate Voltage in GaAs/AlGaAs Wires

The magneto-transport properties of two-dimensional electron gas (2DEG) at high magnetic fields and low temperatures are related to the edge and bulk states. These states cause nonlocal effects, such as nonlocal Shubnikov-de Haas (SdH) oscillations, and the influence of extra probes on the four-terminal resistance. We observed the selective diminishing of the down spin peak and the up spin peak in nonlocal SdH oscillations and investigated the influence of the extra probes which ostensibly have nothing to do with the four-terminal resistance. The influence of the extra probes on normal and nonlocal SdH measurement is explained by a decrease in the chemical potentials of the edge states at the extra probes.