Coexistence of Bose-Einstein paraexcitons with Maxwell-Boltzmann orthoexcitons inCu2O

Time-resolved photoluminescence studies in ${\mathrm{Cu}}_2$O at high excitation levels and intermediate lattice temperatures (${\mathit{T}}_{\mathit{L}}$≃30 K) exhibit a nearly classical orthoexciton distribution with gas temperature somewhat higher than ${\mathit{T}}_{\mathit{L}}$ during the excitation pulse. Simultaneously, a paraexciton spectrum with width less than half that of the classical distribution is observed during the pulse, indicating the quantum-statistical nature of this high-density component.