Exciton spin relaxation in single semiconductor quantum dots

TL;DR

This paper investigates how exciton spin relaxation times in single semiconductor quantum dots are influenced by size, magnetic field, and temperature, highlighting the roles of exchange interactions and phonons.

Contribution

It provides a detailed theoretical analysis of exciton spin relaxation mechanisms in asymmetrical quantum dots, considering material and external field effects.

Findings

Relaxation times depend strongly on dot size, magnetic field, and temperature.

Zero-field relaxation times are long at low temperatures but decrease under high magnetic fields.

Material composition influences relaxation dynamics, with (In,Ga)As and (Cd,Zn)Se quantum dots analyzed.

Abstract

We study the relaxation of the exciton spin (longitudinal relaxation time $T_{1}$) in single asymmetrical quantum dots due to an interplay of the short--range exchange interaction and acoustic phonon deformation. The calculated relaxation rates are found to depend strongly on the dot size, magnetic field and temperature. For typical quantum dots and temperatures below 100 K, the zero--magnetic field relaxation times are long compared to the exciton lifetime, yet they are strongly reduced in high magnetic fields. We discuss explicitly quantum dots based on (In,Ga)As and (Cd,Zn)Se semiconductor compounds.