Stimulated cooling in non-equilibrium Bose-Einstein condensate

Abstract We report on the experimental observation of stimulated cooling in the non-equilibrium Bose--Einstein condensate (BEC) of weakly interacting exciton-polaritons from approximately room temperature down to 20K. Our results indicate that the temperature of the weakly interacting Bose gas is universally set by the density-dependent chemical potential, revealing a defining property of non-equilibrium BECs. We demonstrate that the stimulated nature of the cooling process directly governs the emergence of quantum coherence of the condensate and shapes the dissipative properties of the excited states.