Spin-Hall effect in two-dimensional mesoscopic hole systems

TL;DR

This paper investigates the spin Hall effect in two-dimensional hole systems, demonstrating its robustness and dependence on various parameters, and showing it can generate pure spin currents without initial spin polarization.

Contribution

It provides a detailed analysis of the spin Hall effect in 2D hole systems using Landauer-Büttiker formalism, revealing robustness against disorder and independence from spin-up/down correlations.

Findings

Spin Hall effect exists without spin-up/down correlations.

Pure spin currents can be generated from charge currents.

Spin Hall coefficients depend on Fermi energy, size, and disorder.

Abstract

The spin Hall effect in two dimensional hole systems is studied by using the four-terminal Landauer-B\"{u}ttiker formula with the help of Green functions. The spin Hall effect exists even when there are {\em not} any correlations between the spin-up and -down heavy holes (light holes) and when the $\Gamma$-point degeneracy of the heavy hole and light hole bands is lifted by the confinement or recovered by the strain. When only a heavy hole charge current without any spin polarization is injected through one lead, under right choice of lead voltages, one can get a pure heavy (light) hole spin current, combined with a possible impure light (heavy) hole spin current from another two leads. The spin Hall coefficients of both heavy and light holes depend on the Fermi energy, devise size and the disorder strength. It is also shown that the spin Hall effect of two dimensional hole systems is much more robust than that of electron systems with the Rashba spin-orbit coupling and the spin Hall coefficients do not decrease with the system size but tend to some nonzero values when the disorder strength is smaller than some critical value.