Weak localization in low-symmetry quantum wells

TL;DR

This paper develops a theory of weak localization in low-symmetry quantum wells, analyzing how spin-orbit interactions and impurity distributions affect magnetoresistance and enabling measurement of spin relaxation times.

Contribution

It presents a comprehensive theory for weak localization in [110] and [111] quantum wells, including effects of bulk inversion asymmetry and random Rashba coupling.

Findings

Negative magnetoresistance due to bulk inversion asymmetry.

Cubic momentum spin-orbit coupling suppresses weak localization.

Expressions for electron spin relaxation times from transport data.

Abstract

Theory of weak localization is developed for electrons in semiconductor quantum wells grown along [110] and [111] crystallographic axes. Anomalous conductivity correction caused by weak localization is calculated for symmetrically doped quantum wells. The theory is valid for both ballistic and diffusion regimes of weak localization in the whole range of classically weak magnetic fields. We demonstrate that in the presence of bulk inversion asymmetry the magnetoresistance is negative: The linear in the electron momentum spin-orbit interaction has no effect on the conductivity while the cubic in momentum coupling suppresses weak localization without a change of the correction sign. Random positions of impurities in the doping layers in symmetrically doped quantum wells produce electric fields which result in position-dependent Rashba coupling. This random spin-orbit interaction leads to spin relaxation which changes the sign of the anomalous magnetoconductivity. The obtained expressions allow determination of electron spin relaxation times in (110) and (111) quantum wells from transport measurements.