 Exciton-polariton condensate

An exciton-polariton condensate has coherent macroscopic occupation of an exciton–photon hybrid mode. Finite photon lifetime makes it an open system: pumping a noncondensed reservoir can replenish condensate losses. A condensate equation coupled to a reservoir-rate equation describes gain saturation, interaction shifts and reservoir feedback; it need not possess a conserved Hamiltonian.