Universal spin-Hall conductance fluctuations in two dimensions

TL;DR

This paper theoretically investigates spin-Hall conductance fluctuations in disordered two-dimensional systems, revealing a universal fluctuation value in the diffusive regime that is independent of specific spin-orbit interactions.

Contribution

It identifies a universal spin-Hall conductance fluctuation in 2D disordered systems, independent of the type of spin-orbit interaction, and characterizes its dependence on spin-orbit coupling strength.

Findings

Universal conductance fluctuation value of ~0.18 e/4π in the diffusive regime.

Fluctuation value depends on spin-orbit coupling strength, not on system parameters.

Distribution of conductance transitions from Gaussian to non-Gaussian with increasing disorder.

Abstract

We report a theoretical investigation on spin-Hall conductance fluctuation of disordered four terminal devices in the presence of Rashba or/and Dresselhaus spin-orbital interactions in two dimensions. As a function of disorder, the spin-Hall conductance $G_{sH}$ shows ballistic, diffusive and insulating transport regimes. For given spin-orbit interactions, a universal spin-Hall conductance fluctuation (USCF) is found in the diffusive regime. The value of the USCF depends on the spin-orbit coupling $t_{so}$, but is independent of other system parameters. It is also independent of whether Rashba or Dresselhaus or both spin-orbital interactions are present. When $t_{so}$ is comparable to the hopping energy $t$, the USCF is a universal number $\sim 0.18 e/4\pi$. The distribution of $G_{sH}$ crosses over from a Gaussian distribution in the metallic regime to a non-Gaussian distribution in the insulating regime as the disorder strength is increased.