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

PACS 72.25.Dc – Spin polarized transport in semiconductors 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. Copyright c © EPLA, 2012 Introduction. – The spin-orbit interaction (SOI) is a remarkable example of an “emergent interaction”. For electrons in vacuum, the SOI emerges from the projec-tion of the Dirac equation on positive energy states. It is intrinsically weak, since its “coupling constant ” contain