Hole spin relaxation during the tunneling between coupled quantum dots

Abstract

We investigate theoretically the spin transport in an array of Ge/Si quantum dots. In the frame of the tight-binding approach we calculate the probability of hole spin-flip for resonant tunneling between localized states in neighboring quantum dots. The tunneling between hole ground states occurs mainly with conservation of the spin. For excited states the probability of the spin-flip is higher. We find that the main source of the spin-flip is the structure-inversion asymmetry (SIA) of the Ge quantum dot. Every tunneling event is accompanied by the small rotation of the angular momentum and this provokes the spin-flip. Simple estimations of the time of spin relaxation caused by the SIA-mechanism give ${\ensuremath{\tau}}_{\mathrm{SIA}}\ensuremath{\sim}{10}^{\ensuremath{-}5}\phantom{\rule{0.3em}{0ex}}\mathrm{s}$.