Exciton energy renormalisation due to the biexciton gas

Summary form only given. Energy renormalisation of the excitonic resonance due to excitonic correlations within the electron gas in semiconductors is well-known. Higher order correlations give rise to quasi-particles such as biexcitons, yet the energy renormalisations associated with these are unknown. In order to follow the dynamics of both the biexciton population and its effect on the exciton resonance we have extended the technique of pump-continuum probe spectroscopy to include circular polarisation of both pump and probe pulses. For ZnSe-ZnCdSe-ZnSe quantum wells at 4K, we demonstrate that the coefficient expressing the formation of biexcitons from a gas comprising equal fractions of both optically-active exciton spin-states.