BIEXCITON AND TRIEXCITON STATES IN QUANTUM DOTS IN THE WEAK CONFINEMENT REGIME

Biexciton and triexciton states in CuCl quantum dots were studied by m eans of time-resolved size-selective pump-and-probe technique. A clear induced absorption band is observed on the high-energy side of the ex citation photon energy. The new induced absorption is assigned to the transition from the exciton ground state to one of the weakly correlat ed exciton pair states which were theoretically predicted to exist and to play an important role in nonlinear optical processes. Its pump en ergy dependence and temporal evolution strongly support this assignmen t. Under high-density or two-color excitation condition, a triexciton state in quantum dots is observed for the first time.