Ground-state and spectral signatures of cavity exciton-polariton condensates

TL;DR

This paper introduces a projector-based renormalization method to analyze exciton-polariton Bose-Einstein condensation in microcavities, revealing a crossover from excitonic insulator to polariton and photonic states influenced by detuning and excitation density.

Contribution

It presents a novel theoretical framework that treats Coulomb interactions and light-matter coupling on equal footing to study ground-state and spectral properties of exciton-polariton condensates.

Findings

Crossover from excitonic insulator to polariton and photonic condensates with increasing excitation density.

Significant quasiparticle band renormalization affecting luminescence spectra.

Flat bottom in wavevector-resolved luminescence spectrum at small detuning.

Abstract

We propose a projector-based renormalization framework to study exciton-polariton Bose-Einstein condensation in a microcavity matter-light system. Treating Coulomb interaction and electron-hole/photon coupling effects on an equal footing we analyze the ground-state properties of the exciton polariton model according to the detuning and the excitation density. We demonstrate that the condensate by its nature shows a crossover from an excitonic insulator (of Bose-Einstein respectively BCS type) to a polariton and finally photonic condensed state as the excitation density increases at large detuning. If the detuning is weak polariton or photonic phases dominate. While in both cases a notable renormalization of the quasiparticle band structure occurs that strongly affects the coherent part of the excitonic luminescence, the incoherent wavevector-resolved luminescence spectrum develops a flat bottom only for small detuning.