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.
@article{arxiv.1001.1235,
title = {Spin-orbit coupling induced by a mass gradient},
author = {A. Matos-Abiague},
journal= {arXiv preprint arXiv:1001.1235},
year = {2015}
}