Spin dynamics of low-dimensional excitons due to acoustic phonons

Abstract

We investigate the spin dynamics of excitons interacting with acoustic phonons in quantumwells, quantum wires and quantum discs by employing a multiband model based on the4 × 4 Luttinger Hamiltonian. We also use the Bir–Pikus Hamiltonian to model the coupling ofexcitons to both longitudinal acoustic phonons and transverse acoustic phonons,thereby providing us with a realistic framework in which to determine details of thespin dynamics of excitons. We use a fractional dimensional formulation to modelthe excitonic wavefunctions and we demonstrate explicitly the decrease of spinrelaxation time with dimensionality. Our numerical results are consistent withexperimental results of spin relaxation times for various configurations of theGaAs/Al0.3Ga0.7As material system. We find that longitudinal and transverse acoustic phonons are equallysignificant in processes of exciton spin relaxations involving acoustic phonons.