Phonon assisted biexciton generation in a single quantum dot

We investigate phonon assisted absorption of a single InGaAs/GaAs quantum dot by multi-channel photoluminescence excitation spectroscopy as a function of magnetic field. We find strong resonances in the absorption spectra corresponding to GaAs LO phonon assisted generation of exciton and biexciton states. Magnetic field induced detuning of the resonance conditions results in a twofold diagonal splitting of the exciton line. This indicates spin conservation during the phonon assisted absorption process and the successive recombination process. In contrast to the exciton line a symmetric fourfold splitting is observed for the biexciton resonances. These findings are explained in terms of sequential biexciton generation followed by sequential biexciton decay.