Electron-spin beat susceptibility of excitons in semiconductor quantum wells

TL;DR

This paper develops a microscopic theory to explain how electron spin coherence in excitons affects optical responses in quantum wells, matching experimental observations of spin dynamics.

Contribution

It introduces a spin beat susceptibility concept and evaluates it for incoherent excitons, advancing understanding of many-body spin effects in quantum wells.

Findings

Explains parametric dependencies in spin coherence measurements

Defines and evaluates spin beat susceptibility in excitonic gases

Matches theoretical results with experimental data

Abstract

Recent time-resolved differential transmission and Faraday rotation measurements of long-lived electron spin coherence in quantum wells displayed intriguing parametric dependencies. For their understanding we formulate a microscopic theory of the optical response of a gas of optically incoherent excitons whose constituent electrons retain spin coherence, under a weak magnetic field applied in the quantum well's plane. We define a spin beat susceptibility and evaluate it in linear order of the exciton density. Our results explain the many-body physics underlying the basic features observed in the experimental measurements.