Non-linear in-plane spin current in spin-orbit coupled 2D hole gases

TL;DR

This paper demonstrates the existence of non-linear in-plane spin currents in 2D hole gases with spin-orbit coupling, revealing new mechanisms for spin current generation and control relevant for spintronics.

Contribution

It introduces a theoretical framework showing second-order in-plane spin currents arise from spin Berry curvature in 2D systems, including effects of anisotropic spin-orbit couplings.

Findings

Second-order in-plane spin current exists in 2D systems with time-reversal symmetry.

Anisotropic spin-orbit couplings can produce collinearly polarized spin currents.

Electromagnetic radiation influences spin current generation and control.

Abstract

The non-linear transport of charge and spin due to the emergence of band geometric effects has garnered much interest in recent years. In this work, we show that a linear in-plane spin current vanishes, whereas a non-linear (second-order) in-plane spin current exists for a generic two-dimensional system having time-reversal symmetry. The intrinsic second-order spin current originates from the spin Berry curvature polarizability. The formulation when applied to 2D hole gases with the $k^3$ Rashba spin-orbit coupling reveals the existence of both transverse and longitudinal second-order spin currents normal to the spin orientation. Interestingly, anisotropic spin-orbit couplings can generate collinearly polarized spin current (spins polarized in the direction of spin current) in the second-order. The effects of anisotropy are explored by introducing an additional Dresselhaus spin-orbit coupling and electromagnetic radiation over the isotropic Rashba system. The generation and control over the multiple in-plane spin currents may have important applications in spintronic devices.