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

Oleg Chalaev^1a, G. Vignale¹ and Michael E. Flatté²

¹ Department of Physics and Astronomy, University of Missouri - Columbia, MO 65211, USA
² Optical Science and Technology Center and Department of Physics and Astronomy, University of Iowa Iowa City, IA 52242, USA

^a chalaev@gmail.com

Received: 31 December 2011
Accepted: 12 March 2012

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 U_ext/E_g≪1 (where U_ext is the pseudopotential of an interstitial atom, and E_g 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.