Hole Spin Helix: Anomalous Spin Diffusion in Anisotropic Strained Hole Quantum Wells

TL;DR

This paper investigates how strain and anisotropy affect spin-orbit interactions and spin diffusion in hole quantum wells, revealing conditions for enhanced spin lifetime and persistent spin helix formation.

Contribution

It introduces a simplified two-band model capturing strain and anisotropy effects, predicting enhanced spin lifetimes and spin helix phenomena in hole systems.

Findings

Strain induces a Rashba term in hole spin-orbit coupling.

Anisotropy introduces a Dresselhaus-like term.

Enhanced spin lifetime associated with a spin helix.

Abstract

We obtain the spin-orbit interaction and spin-charge coupled transport equations of a two-dimensional heavy hole gas under the influence of strain and anisotropy. We show that a simple two-band Hamiltonian can be used to describe the holes. In addition to the well-known cubic hole spin-orbit interaction, anisotropy causes a Dresselhaus-like term, and strain causes a Rashba term. We discover that strain can cause a shifting symmetry of the Fermi surfaces for spin up and down holes. We predict an enhanced spin lifetime associated with a spin helix standing wave similar to the Persistent Spin Helix which exists in the two-dimensional electron gas with equal Rashba and Dresselhaus spin-orbit interactions. These results may be useful both for spin-based experimental determination of the Luttinger parameters of the valence band Hamiltonian and for creating long-lived spin excitations.