Spin dynamics of low-dimensional excitons due to acoustic phonons

TL;DR

This paper studies how exciton spin relaxation times vary with dimensionality in low-dimensional semiconductor structures, using advanced models to incorporate acoustic phonon interactions and matching experimental data.

Contribution

It introduces a multiband model with realistic phonon coupling to analyze exciton spin dynamics across different low-dimensional systems, highlighting the impact of dimensionality.

Findings

Spin relaxation time decreases with lower dimensionality.

Longitudinal and transverse acoustic phonons equally influence spin relaxation.

Numerical results align with experimental data for GaAs/AlGaAs systems.

Abstract

We investigate the spin dynamics of excitons interacting with acoustic phonons in quantum wells, quantum wires and quantum disks by employing a multiband model based on the $4\times4$ Luttinger Hamiltonian. We also use the Bir-Pikus Hamiltonian to model the coupling of excitons to both longitudinal acoustic phonons and transverse acoustic phonons, thereby providing us with a realistic framework in which to determine details of the spin dynamics of excitons. We use a fractional dimensional formulation to model the excitonic wavefunctions and we demonstrate explicitly the decrease of spin relaxation time with dimensionality. Our numerical results are consistent with experimental results of spin relaxation times for various configurations of the GaAs/Al$_{0.3}$Ga$_{0.7}$As material system. We find that longitudinal and transverse acoustic phonons are equally significant in processes of exciton spin relaxations involving acoustic phonons.