Spin-orbit interaction from low-symmetry localized defects in semiconductors

TL;DR

This paper reveals a new extrinsic spin-orbit interaction caused by low-symmetry defects in semiconductors, which can significantly influence spin relaxation rates even at moderate impurity levels.

Contribution

It introduces a novel first-order extrinsic spin-orbit term arising from defect potentials, expanding understanding of spin dynamics in semiconductors.

Findings

The new spin-orbit interaction is proportional to defect potential matrix elements.

It can dominate previous extrinsic contributions to spin relaxation.

The effect is significant even at moderate impurity concentrations.

Abstract

The presence of low-symmetry impurities or defect complexes in the zinc-blende direct-gap semiconductors (e.g. interstitials, DX-centers) results in a novel spin-orbit term in the effective Hamiltonian for the conduction band. The new extrinsic spin-orbit interaction is proportional to the matrix element of the defect potential between the conduction and the valence bands. Because this interaction arises already in the first order of the expansion of the effective Hamiltonian in powers of Uext/Eg << 1 (where Uext is the pseudopotential of an interstitial atom, and Eg is the band gap), its contribution to the spin relaxation rate may exceed that of the previously studied extrinsic contributions, even for moderate concentrations of impurities.