Kinetics of indirect excitons in an optically induced trap in GaAs quantum wells

We report on the kinetics of a low-temperature gas of indirect excitons in an optically induced exciton trap. The excitons in the region of laser excitation are found to rapidly-within 4 ns-cool to the lattice temperature T=1.4 K, while the excitons at the trap center are found to be cold-essentially at the lattice temperature-even during the excitation pulse. The loading time of excitons to the trap center is about 40 ns, longer than the cooling time yet shorter than the lifetime of the indirect excitons. The observed time hierarchy is favorable for creating a dense and cold exciton gas in optically induced traps and for in situ control of the gas by varying the excitation profile in space and time before the excitons recombine.