Exact Analytical Solution for the Density Matrix of a Nonequilibrium Polariton Bose-Einstein Condensate

• DOI: 10.1103/physrevlett.128.065301
• Publication Date: 2022-02-10T15:06:16Z
• Authors: Vladislav Yu. Shi...; Evgeny S. Andrianov; Anton V. Zasedatelev; Pavlos G. Lagoudakis; Yurii E. Lozovik
• Keywords: Quantum Physics; Condensed Matter - Mesoscale and Nanoscale Physics; Statistical Mechanics (cond-mat.stat-mech); FOS: Physical sciences; 02 engineering and technology; 530; 01 natural sciences; Quantum Gases (cond-mat.quant-gas); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); 0103 physical sciences; Condensed Matter - Quantum Gases; 0210 nano-technology; Quantum Physics (quant-ph); Condensed Matter - Statistical Mechanics

In this letter, we give an analytical quantum description of a non-equilibrium polariton Bose-Einstein condensate (BEC) based on the solution of the master equation for the full polariton density matrix in the limit of fast thermalization. We find the density matrix of a non-equilibrium BEC, that takes into account quantum correlations between all polariton states. We show that the formation of BEC is accompanied by the build-up of cross-correlations between the ground state and the excited states reaching their highest values at the condensation threshold. Despite the non-equilibrium nature of polariton systems, we show the average population of polariton states exhibits the Bose-Einstein distribution with an almost zero effective chemical potential above the condensation threshold similar to an equilibrium BEC. We demonstrate that above threshold the effective temperature of polariton condensate drops below the reservoir temperature.