Nonlinear paraexciton kinetics in a potential trap inCu2Ounder two-photon resonance excitation

Abstract

The nonlinear kinetics of paraexcitons confined in a harmonic trap in ${\mathrm{Cu}}_{2}\mathrm{O}$ is examined by analyzing emission spectra under two-photon excitation of orthoexcitons as a function of the excitation power density. Strong saturation has been observed in paraexciton density without saturation of orthoexciton density. This indicates the occurrence of two-body collision that works as evaporative cooling process in the trap. We also show evidence for the direct creation of cold paraexcitons by a two-photon resonance excitation.