Energy spectrum of negatively charged single quantum dot: trion and charged biexciton states

We have studied the energy spectrum of negatively charged single CdSe quantum dots using two-beam photoluminescence excitation spectroscopy. We observe bleaching of the linear trion spectrum and appearance of induced absorption due to excitation of charged biexciton states. The data embody clear signatures for Pauli blocking, many-particle Coulomb interactions as well as electron–hole exchange fine structure.