Spin orientation by electric current in (110) quantum wells

TL;DR

This paper develops a comprehensive theory of spin orientation by electric current in (110) quantum wells, resolving previous controversies and exploring effects of energy relaxation, structural asymmetry, and topological insulators.

Contribution

It introduces a unified framework considering energy relaxation effects and spatial fluctuations, advancing understanding of spin polarization mechanisms in quantum wells.

Findings

Spin orientation depends on energy relaxation rates and spatial fluctuation correlation length.

Symmetric quantum wells exhibit spin orientation due to Rashba splitting fluctuations.

Spin polarization kinetics are non-exponential at slow energy relaxation.

Abstract

We develop a theory of spin orientation by electric current in (110)-grown semiconductor quantum wells. The controversy in the factor of two from two existed approaches is resolved by pointing out the importance of energy relaxation in this problem. The limiting cases of fast and slow energy relaxation relative to spin relaxation are considered for asymmetric (110) quantum wells. For symmetricly-doped structures the effect of spin orientation is shown to exist due to spatial fluctuations of the Rashba spin-orbit splitting. We demonstrate that the spin orientation depends strongly on the correlation length of these fluctuations as well as on the ratio of the energy and spin relaxation rates. The time-resolved kinetics of spin polarization by electric current is also governed by the correlation length being not purely exponential at slow energy relaxation. Electrical spin orientation in two-dimensional topological insulators is calculated and compared with the spin polarization induced by the magnetic field.