Electric generation of spin in crystals with reduced symmetry

TL;DR

This paper introduces a straightforward method to evaluate bulk spin generation in crystals with strong spin-orbit coupling, highlighting an intrinsic torque effect that can be experimentally observed across various crystal structures.

Contribution

It presents a novel, simple approach to calculate spin generation in arbitrary crystals, emphasizing the intrinsic torque mechanism under electric fields.

Findings

Intrinsic torque leads to nonzero spin generation rate.

Method applicable to various crystal structures including wurtzite and zincblende.

Spin polarization can be experimentally measured.

Abstract

We propose a simple way of evaluating the bulk spin generation of an arbitrary crystal with a known band structure in the strong spin-orbit coupling limit. We show that, in the presence of an electric field, there exists an intrinsic torque term which gives rise to a nonzero spin generation rate. Using methods similar to those of recent experiments which measure spin polarization in semiconductors, this spin generation rate should be experimentally observable. The wide applicability of this effect is emphasized by explicit consideration of a range of examples: bulk wurtzite and strained zincblende (n-GaAs) lattices, as well as quantum well heterojunction systems.