Role of dark excitations in the nonequilibrium condensation of exciton polaritons in optically-pumped organic single crystal microcavities

Abstract

We present a reaction/diffusion model for the formation of a lower polariton condensate in a microcavity 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 dark states formed by the nonemissive decay of excitons in to nearby electronic states, and a lower polariton condensate. We show that at finite temperature, the presence of the dark reservoir can augment the exciton population such that a lower critical pumping threshold is required to achieve the critical exciton densities required to sustain a stable condensate population. Using linear-stability analysis, we show that a variety of dynamical regimes can emerge depending upon the characteristics of the cavity and the lattice temperature.