A new aspect of the Bose-Einstein condensation of 1s-exciton system in Cu2O

Abstract Bose-Einstein statistics of is ortho- and para-excitons in commercially available natural single crystals of Cu 2 O is examined by spectral shape analysis of their phonon assisted emissions under a band-to-band excitation. It is confirmed that the density of the ortho-excitons increases with the rise of the effective temperature along the phase transition boundary as the power density of the excitation light increases. It is newly found that the density of the para-excitons stays at the critical density of the BEC at 3K in the excitation power density between 10 2 W/cm 2 and 6 × 10 4 W/cm 2 .