Spin Hall effect in Rashba-Dresselhaus planar strips in the presence of electron correlations

TL;DR

This paper investigates the spin Hall effect in Rashba-Dresselhaus systems with electron correlations, revealing nonmonotonic behaviors and interaction-enhanced spin currents through theoretical and numerical methods.

Contribution

It introduces a combined analysis of spin Hall conductivity and electron interactions in Rashba-Dresselhaus strips using linear response and DMRG methods.

Findings

Nonmonotonic spin Hall conductivity as a function of SO coupling ratio.

Hubbard interactions enhance spin currents and accumulation.

Similar nonmonotonic behavior observed out-of-equilibrium with bias.

Abstract

A model with both Rashba and Dresselhaus spin orbit (SO) couplings and Hubbard electron-electron interaction is studied on planar strips at quarter filling at zero temperature in the clean limit. In the absence of Hubbard repulsion and at equilibrium, within linear response theory, a nonmonotonic behavior of the spin Hall conductivity as a function of the ratio of the Rashba (alpha) and Dresselhaus (beta) strengths was found for large enough SO strengths. This behavior is signalled by a peak or a cusp, depending on the strip width, at intermediate values of beta/alpha in the interval [0,1]. This behavior of the spin Hall conductivity was correlated with the one for the longitudinal spin conductivity. This study was then extended to the out-of-equilibrium regime that arises by imposing a finite voltage bias between the two ends of an open strip. This system, in the presence of a Hubbard term with coupling U, was treated with the density matrix renormalization group technique and with the Landauer-Buttiker formalism. It was found that relevant properties to the spin Hall effect, such as the transversal spin current and the spin accumulation, present a similar nonmonotonic behavior as the one found for the spin conductivities. More importantly, it was also found that these properties are enhanced by the repulsive Hubbard interaction up to a moderate value of U.