Luminescence of a “Cold” gas of biexcitons in CuCl

Abstract

Abstract The emission due to the radiative decay of biexcitons in CuCl is studied at low temperatures. Biexcitons formed of free excitons mainly under LO phonon emission, contribute to the broad emission bands observed. In the case of direct creation of biexcitons by resonant two‐photon absorption, a “cold” biexciton gas is created which is not in thermal equilibrium and gives rise to the narrow emission lines. A Bose‐Einstein condensation of the biexcitons seems to be very unlikely.