Dominant role of the shear strain induced admixture in spin-flip processes in self-assembled quantum dots

We study theoretically the spin-flip relaxation processes for a single electron in a self-assembled InAs/GaAs quantum dot, and we show that the dominant channel is the spin admixture induced by symmetry-breaking shear strain. This mechanism, determined within the eight-band envelope-function k·p theory, can be mapped onto two effective spin-phonon terms in a conduction-band (effective-mass) Hamiltonian that have a similar structure and interfere constructively. Unlike the Dresselhaus coupling, which dominates spin relaxation in larger, unstrained dots, the shear strain contribution cannot be modeled by a generic, standard term in the Hamiltonian but rather relies on the actual strain distribution in the quantum dot.