Quantum mechanical repulsion of exciton levels in a disordered quantum well evidenced by near-field spectroscopy

Near-field photoluminescence spectra of a single quantum well dominated by emission from localized excitons are subjected to a statistical analysis of the two-energy autocorrelation function. This analysis is compared to a theoretical model of the exciton center-of-mass motion in a two-dimensional spatially correlated disordered potential. The spatial and energetic parameters of the disorder potential underlying the excitonic motion are extracted and clear signatures of quantum-mechanical energy level repulsion are revealed.