Exciton-exciton interaction and biexcitons in the presence of spin-polarized carriers

摘要

We present an absorption study of the neutral exciton, biexciton and positively charged exciton (trion) in a (Cd,Mn)Te quantum well under the influence of a femtosecond, circularly polarized, resonant pump pulse. By using spin-dependent selection rules in a quantum well containing a strongly diluted magnetic semiconductor, we could unambiguously separate the biexcitonic transitions from the charged exciton ones, and we report on their simultaneous observation for a well chosen configuration of the pump and probe polarization. The influence of the hole gas on the biexciton line is described. In a polarization such as the charged exciton line is not present in the transmission spectrum, the sum of the neutral exciton and biexciton intensities is conserved, whatever the density of preexisting holes. However, when both the charged exciton and the biexciton coexist, we observed some intensity stealing from the biexciton by the charged exciton.