Polariton–polariton kinematic interaction modulation and kinematic bipolaritons in organic microcavities

We study polariton–polariton kinematic interactions in organic microcavities. Using the Agranovich–Toshich transformation, to transform the Frenkel excitons from Paulions into Bosons, the exciton–exciton kinematic interaction is derived. In the strong coupling regime, the polariton excitonic part results in the polariton–polariton kinematic interaction. The scattering amplitude is calculated and the effective potential is obtained for a scattering between two free polaritons. The effective potential can be modulated by changing the exciton-cavity photon detuning, and we show the crossover of the effective potential from attractive into repulsive one. A pole in the two-particle Green's function is the signature of the formation of polariton bound state, i.e. bipolariton. Due to the smallness of the polariton effective mass, the obtained bound state is very shallow and appears below the minimum of the lower polariton branch, and falls inside the natural bandwidth of the polariton branch.