Coherent and non-Markovian effects in ultrafast relaxation of photoexcited hot carriers: A model study.

We discuss two quantum effects that can influence the relaxation of carriers in a semiconductor excited by an ultrashort light pulse. Namely, the presence of nonzero interband optical polarization and the large energy uncertainty of carriers created by the short exciting pulse. The importance of both effects is investigated numerically for the case of electron\char21{}LO-phonon interaction assuming a model (exponential) pulse shape. Comparison of the results with the predictions based on the conventional Boltzmann equation indicates that both effects lead to a much more even distribution of carriers over k space, which may significantly shorten thermalization times.