Edge spin accumulation in semiconductor two-dimensional hole gases

TL;DR

This paper investigates the intrinsic spin Hall effect in two-dimensional hole gases, demonstrating large, localized edge spin accumulations that are independent of disorder and device width, confirmed through experiments.

Contribution

It reveals the intrinsic nature of edge spin accumulation in 2D hole gases and its dependence on spin-orbit coupling, supported by numerical and experimental evidence.

Findings

Large edge spin polarization induced by spin Hall effect

Spin accumulation increases with spin-orbit coupling strength

Edge localization is independent of device width beyond mean-free-path

Abstract

The controlled generation of localized spin densities is a key enabler of semiconductor spintronics In this work, we study spin Hall effect induced edge spin accumulation in a two-dimensional hole gas with strong spin orbit interactions. We argue that it is an intrinsic property, in the sense that it is independent of the strength of disorder scattering. We show numerically that the spin polarization near the edge induced by this mechanism can be large, and that it becomes larger and more strongly localized as the spin-orbit coupling strength increases, and is independent of the width of the conducting strip once this exceeds the elastic scattering mean-free-path. Our experiments in two-dimensional hole gas microdevices confirm this remarkable spin Hall effect phenomenology. Achieving comparable levels of spin polarization by external magnetic fields would require laboratory equipment whose physical dimensions and operating electrical currents are million times larger than those of our spin Hall effect devices.