Theory of vibronic assistance in the nonequilibrium condensation of exciton polaritons in optically--pumped organic single crystal microcavities

We present a reaction/diffusion model for the formation of a lower polariton condensate in a micro cavity containing an organic semiconducting molecular crystalline film. Our model--based upon an anthracene film sandwiched between two reflecting dielectric mirrors--consists of three coupled fields corresponding to a gas of excitons created by an external driving pulse, a reservoir of vibron states formed by the coupling between a ground-state vibrational model and a cavity photon, and a lower polariton condensate. We show that at finite temperature, the presence of the vibron reservoir can augment the exciton population such that a lower critical pumping threshold is required to achieve condensation.