Absorption, Photoluminescence and Resonant Rayleigh Scattering Probes of Condensed Microcavity Polaritons

TL;DR

This paper compares optical probes of microcavity polariton condensation, highlighting the effectiveness of resonant Rayleigh scattering in revealing collective modes and disorder effects, with implications for understanding polariton behavior.

Contribution

It introduces a comprehensive analysis of optical responses, especially resonant Rayleigh scattering, accounting for disorder effects in microcavity polariton condensates.

Findings

Resonant Rayleigh scattering distinctly probes condensation phenomena.

Disorder significantly influences optical responses and must be considered to all orders.

Linear blue-shift of polaritons depends on temperature and disorder length.

Abstract

We investigate and compare different optical probes of a condensed state of microcavity polaritons in expected experimental conditions of non-resonant pumping. We show that the energy- and momentum-resolved resonant Rayleigh signal provide a distinctive probe of condensation as compared to, e.g., photoluminescence emission. In particular, the presence of a collective sound mode both above and below the chemical potential can be observed, as well as features directly related to the density of states of particle-hole like excitations. Both resonant Rayleigh response and the absorption and photoluminescence, are affected by the presence of quantum well disorder, which introduces a distribution of oscillator strengths between quantum well excitons at a given energy and cavity photons at a given momentum. As we show, this distribution makes it important that in the condensed regime, scattering by disorder is taken into account to all orders. We show that, in the low density linear limit, this approach correctly describes inhomogeneous broadening of polaritons. In addition, in this limit, we extract a linear blue-shift of the lower polariton versus density, with a coefficient determined by temperature and by a characteristic disorder length.