Short note on the excitonic Mott phase

An exciton gas on a lattice is analyzed in terms of a convergent hopping expansion. For a given chemical potential our calculation provides a sufficient condition for the hopping rate to obtain an exponential decay of the exciton correlation function. This result indicates the existence of a Mott phase in which strong fluctuations destroy the long range correlations in the exciton gas at any temperature, either by thermal or by quantum fluctuations.