The role of coherent momentum evolution in biexcitonic luminescence from GaAs quantum wells

Summary form only given. In this paper we present time-resolved photoluminescence (PL) studies of biexcitons in GaAs quantum wells (QW) with femtosecond resolution. Using polarization selection rules for biexcitons, we separate the biexciton PL from the exciton PL while still retaining adequate time resolution. A surprising initial transient characterized by a finite rise and an extremely fast decay is revealed in the biexciton PL. We show that this initial transient stems from coherent quantum evolution of relative momentum of two excitons in the molecule, in sharp contrast to the initial dynamics of exciton radiative recombination. The initial transient also reflects a type of quantum beat that differs from the usual quantum beats in transient optical measurements.