Spin-splitting in GaAs 2D holes

Abstract

We present quantitative measurements and calculations of the spin-orbit induced zero-magnetic-field spin-splitting in two-dimensional (2D) hole systems in modulation-doped GaAs (311)A quantum wells. The results show that the splitting is large and tunable. In particular, via a combination of back- and front-gate biases, we can tune the splitting while keeping the 2D hole density constant. The data also reveal a surprising result regarding the magnetoresistance (Shubnikov-de Haas) oscillations in a 2D system with spin-split energy bands: the frequencies of the oscillations are {\it not} simply related to the population of the spin-subbands. Next we concentrate on the metallic-like behavior observed in these 2D holes and its relation to spin-splitting. The data indicate that the metallic behavior is more pronounced when two spin-subbands with unequal populations are occupied. Our measurements of the magnetoresistance of these 2D hole systems with an in-plane magnetic field corroborate this conclusion: while the system is metallic at zero magnetic field, it turns insulating when one of the spin-subbands is depopulated at high magnetic field.

To be published in Physica E, as part of the proceedings of the 11th International Winterschool on New Developments in Solid State Physics held in Mauterndorf, Austria, February, 2000