Coherent ultrafast optical dynamics of the Fermi-edge singularity

We develop a nonequilibrium many-body theory of the coherent femtosecond nonlinear optical response of the Fermi-edge singularity. We study the role of the dynamical Fermi-sea response in the time evolution of the pump-probe spectra. The electron-hole correlations are treated nonperturbatively with the time-dependent coupled cluster expansion combined with the effective Hamiltonian approach. For short pulse durations, we find a nonexponential decay of the differential transmission during negative time delays, which is governed by the interactions. This is in contrast to the results obtained within the Hartree-Fock approximation, which predicts an exponential decay governed by the dephasing time. We discuss the role of the optically induced dephasing effects in the coherent regime. (c) 2000 The American Physical Society.