Two-polariton decay of excitonic molecules

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Abstract
We have studied theoretically the two-polariton decay of excitonic molecules at temperatures of the order of 2 K. In contrast to previous theories on polariton effects in the decay of excitonic molecules, we find that the emission of two photonlike polaritons is an important recombination channel. This decay leads to an extended low-energy continuum in the calculated spontaneous-emission spectrum and to a strong dependence of the radiative lifetime on kinetic energies below 0.1 meV for typical semiconductors. When compared with previous experiments our results suggest that stimulation effects or other nonequilibrium phenomena play an important role.