Bosonic stimulation of cold excitons in a harmonic potential trap in Cu2O

A high-density cold exciton gas is generated in a harmonic potential trap by two-photon resonance excitation of Cu2O at 2 K. Strongly localized light signal is observed at the bottom of the potential trap when the exciton density exceeds 1017 cm-3. The possibility of bosonic stimulation of excitons from the trap rim to the bottom is discussed in connection with the origin of the light signal.