Exciton spin dynamics in GaSe

TL;DR

This study investigates exciton spin dynamics in GaSe using a rate-equation model that accurately reproduces polarization measurements and reveals biexponential spin relaxation at low temperature.

Contribution

The paper introduces a rate-equation model that captures exciton spin relaxation behavior in GaSe, including biexponential decay at 10 K, aligning with experimental photoluminescence data.

Findings

Polarization approaches unity with 0.15 eV excess energy.

Biexponential decay of exciton spin relaxation at 10 K.

Distinct spin-relaxation rates for hot and cold excitons.

Abstract

We analyze exciton spin dynamics in GaSe under nonresonant circularly polarized optical pumping with an exciton spin-flip rate-equation model. The model reproduces polarized time-dependent photoluminescence measurements in which the initial circular polarization approaches unity even when pumping with 0.15 eV excess energy. At T = 10 K, the exciton spin relaxation exhibits a biexponential decay with a sub-20 ps and a >500 ps time constants, which are also reproduced by the rate-equation model assuming distinct spin-relaxation rates for hot (nonequilibrium) and cold band-edge excitons.