Spin dynamics of excited trion states in a single InAs quantum dot

We measure photon cross-correlation between two positively charged biexcitonic emission lines and a positively charged excitonic line for a single InAs/GaAs quantum dot (QD). Marked difference in the correlation function is observed, which originates from multiple spin configurations of intermediate states, i.e., excited positively charged exciton (trion) states. With the aid of a rate equation simulation, we evaluate the transition rate with p -shell hole-spin flip to be 0.8-1.0 GHz, which is almost comparable to the radiative decay rate of the ground charged exciton, presumably due to the spin scattering between carriers in a QD and a wetting layer and/or mixing of the excited trion states. In contrast, the relaxation rate with conserving p -shell hole-spin projection is estimated to be about one order of magnitude higher than that with hole-spin flip.