Combined effect of exciton–exciton and exciton–phonon interaction on crystal's dielectric properties

Abstract

The two-time temperature Green functions method is used to investigate the combined effect of the exciton–exciton and the exciton–phonon interactions on the dielectric properties of the molecular crystals. It is shown that those effects are of the same order of magnitude. The most interesting result is nevertheless the appearance of a double peak in the region ω < ωexciton whereby the narrow peak is due to the exciton–phonon interaction whereas the other, located in the longer wavelength region, is due to the exciton–exciton interaction. The possible further generalization of the results obtained is also discussed.