Carrier relaxation and quantum decoherence of excited states in self-assembled quantum dots

We report systematic measurements of photoluminescence excitation spectra and dephasing times (formula presented) on various excited states of hundreds of individual quantum dots (QDs). From the variation of (formula presented) with the energy separation between excited states and the ground state (formula presented) we identified two distinct regions of (formula presented) where LO phonon emission and hole relaxation via LA phonon emission play as dominat dephasing mechanisms. We also found a clear evidence of significantly slow energy relaxation in the (formula presented) range where these phonon emission processes are suppressed due to the reduction of interaction phase space.