Spin-orbit coupling induced by a mass gradient

TL;DR

This paper reveals a new type of spin-orbit coupling in low-dimensional heterostructures caused by a gradient in effective mass, which can exist independently of electric fields and impacts spin-related phenomena.

Contribution

It introduces the concept of mass-gradient induced spin-orbit coupling in heterostructures, expanding understanding of SOC mechanisms beyond electric field effects.

Findings

Mass-gradient induced SOC exists in asymmetric heterostructures.

This SOC can be finite even without electric fields in graded quantum wells.

The presence of mass gradient influences spin dynamics in low-dimensional systems.

Abstract

The existence of a spin-orbit coupling (SOC) induced by the gradient of the effective mass in low-dimensional heterostructures is revealed. In structurally asymmetric quasi-two-dimensional semiconductor heterostructures the presence of a mass gradient across the interfaces results in a SOC which competes with the SOC created by the electric field in the valence band. However, in graded quantum wells subjected to an external electric field, the mass-gradient induced SOC can be finite even when the electric field in the valence band vanishes.