Spin–orbit interaction and transport in GaAs two-dimensional holes

Abstract

We present quantitative measurements and calculations of the spin–orbit-induced zero magnetic field spin-splitting in GaAs two-dimensional hole systems. The magneto-resistance oscillations in this system show a clear beating pattern which results from the unequal densities of the two spin subbands. We present a Fourier analysis technique that de-convolves the magneto-oscillations of the two subbands. The temperature dependence of the de-convolved oscillations allows us to deduce the effective masses of the subbands without assuming parabolic dispersions for the two subbands. Next, we demonstrate that heavy hole systems in heterostructures exhibit a decrease in spin-splitting with an increase in perpendicular electric field. Our results are in contrast to the more familiar case of electrons where spin-splitting increases with electric field. Another external parameter that effects spin-splitting is strain. We report direct measurements of the spin–orbit interaction-induced spin-splitting in a hole system as a function of anisotropic, in-plane strain. In addition, our piezoresistance measurements reveal a strong dependence on density and the direction along which the resistance is measured. In the end, we present Aharonov–Bohm resistance oscillations in a shallow two-dimensional GaAs hole ring structure, defined by local anodic surface oxidation. The amplitude of the oscillations is about 10% of the ring resistance, the strongest seen in a hole system.