Effects of a few-particle interaction on the atomiclike levels of a single strain-induced quantum dot

We investigate the effects of few-particle population of a single strain-induced quantum dot by optical excitation. The low-power photoluminescence spectra consist of sharp lines with energy separation of a few meV, associated to the formation of excitonic molecules in the single dot. With increasing photoexcitation intensity, the population of higher states is observed; however, we also observe a clear intensity dependence of the transition energies, inconsistent with a simple filling of exciton levels. Based on a theoretical model for interacting electron-hole pairs in the dot, we obtain good agreement with experiment and show that exciton-exciton interactions control the spectral changes as the number of pairs is increased.