Off-diagonal disorder model for exciton polaritons in layered media. Disorder-induced origin of radiative widths

Abstract

Excitons in an infinite layered dipolar medium, such as a layered crystal or a multiple-quantum-well stack, with perfect periodicity exhibit a vanishing radiative width due to the requirement of energy-momentum conservation. Using a polariton model with off-diagonal disorder and a configuration-averaging technique, we show how deviations from the ideal case, specifically in the form of weak departures from perfect periodicity, and the resulting breaking of full translational invariance, give rise to a nonvanishing radiative width.