Spin dependent analysis of homogeneous and inhomogeneous exciton decoherence in magnetic fields

TL;DR

This study investigates how magnetic fields, temperature, and interface properties affect exciton spin coherence in GaAs/AlGaAs quantum wells, revealing complex interactions and non-monotonic coherence behavior at low magnetic fields.

Contribution

It provides a detailed analysis of spin decoherence mechanisms in quantum wells, including the deconvolution of band-gap fluctuations from phonon and interface effects, and uncovers non-monotonic coherence tuning.

Findings

Decoherence mainly due to acoustic phonons and short-range interactions at low powers and temperatures.

Band-gap fluctuations significantly influence decoherence and can be separated from other effects.

Non-monotonic spin coherence behavior observed at low magnetic fields.

Abstract

This paper discusses the combined effects of optical excitation power, interface roughness, lattice temperature, and applied magnetic fields on the spin-coherence of excitonic states in GaAs/AlGaAs multiple quantum wells. For low optical powers, at lattice temperatures between 4 K and 50 K, the scattering with acoustic phonons and short-range interactions appear as the main decoherence mechanisms. Statistical fluctuations of the band-gap however become also relevant in this regime and we were able to deconvolute them from the decoherence contributions. The circularly polarized magneto-photoluminescence unveils a non-monotonic tuning of the coherence for one of the spin components at low magnetic fields. This effect has been ascribed to the competition between short-range interactions and spin-flip scattering, modulated by the momentum relaxation time.