Temperature-dependent superradiant decay of excitons in small aggregates.

Abstract

We investigate the effect of phonons on the cooperative radiative decay of excitons in small aggregates. Our microscopic analysis establishes the existence of a temperature-dependent coherence size, provided the exciton dephasing time scale is much shorter than the fluorescence lifetime ${\mathrm{\ensuremath{\tau}}}_{\mathrm{fl}}$. We calculate the temperature dependenc of ${\mathrm{\ensuremath{\tau}}}_{\mathrm{fl}}$ and use our results to interpret recent photon-echo and fluorescence experiments in strongly coupled J-aggregates of cyanine dye molecules.