Coulomb correlations in quantum dots and their signatures in single dot femtosecond pump-probe signals

We present a theoretical study of femtosecond pump-probe experiments on a negatively charged single quantum dot and analyze the influence of Coulomb correlation effects on the lowest trion absorption line. The Coulomb correlated states as well as their corresponding oscillator strengths are calculated by a full diagonalization approach. The dynamics induced by the laser pulses are determined numerically by solving the Liouville-von Neumann equation in the basis of the calculated few-particle states. In agreement with the experiment, we demonstrate that Coulomb interactions and carrier relaxations noticeably affect the lowest trion absorption line. For negative and short positive delay times between pump and probe pulse instantaneous Coulomb renormalizations dominate the signal while for longer delay times the signal is governed by carrier relaxations.