Nonlinear photoluminescence kinetics of indirect excitons in coupled quantum wells

We report the strongly nonlinear dependence of indirect exciton photolumine scence (PL) kinetics on excitation density. In the indirect regime characte rized by a slow exciton recombination, at high excitation densities, low ma gnetic fields, low temperatures, and for samples with small in-plane disord er, we observe that the indirect exciton PL intensity increases sharply wit hin a few nanoseconds after the excitation is switched off. This PL intensi ty jump is also accompanied by a subsequent PL decay rate that increases wi th excitation density. The effects are observed only when the estimated occ upancies of the lowest energy exciton states exceed unity.