Quantum Fluctuations and Coherence of a Molecular Polariton Condensate

TL;DR

This paper develops a comprehensive quantum theory for exciton polariton condensates, revealing how quantum fluctuations, dark states, and nonclassical photon statistics emerge during nonequilibrium phase transitions driven by pump intensity.

Contribution

It introduces an analytical quantum model beyond mean-field, elucidating the role of dark states and nonclassical statistics in polariton condensation.

Findings

Quantum fluctuations are characterized by an analytical density matrix solution.

A nonequilibrium phase transition is identified with changing pump intensity.

Photon emission exhibits nonclassical counting statistics.

Abstract

A full quantum theory beyond the mean-field regime is developed for an exciton polariton condensate, to gain a complete understanding of quantum fluctuations. We find analytical solution for the polariton density matrix, showing the polariton nonlinearity causing fast relaxation correlated with the pump so as to yield the condensation at threshold. Increasing the pump intensity, a nonequilibrium phase transition towards the condensation of lower polaritons emerges, with a statistics transiting from a thermal, through a super-Poissonian and to a nonclassical distribution beyond the understanding at the level of off-diagonal long-range order. The results signify the role of dark states for polariton fluctuations, and lead to a nonclassical counting statistics of emitted photons, which elaborates the role of the key parameters, e.g., pump, detuning and temperature.