Screened Coulomb quantum kinetics for resonant femtosecond spectroscopy in semiconductors

Abstract

We apply the non-Markovian quantum kinetics of carrier relaxation scattering due to carrier-carrier and carrier-LO-phonon interactions to an electron-hole gas in a semiconductor excited resonantly by coherent femtosecond laser pulses. Our theory employs the full two-time-dependent random-phase approximation (RPA) screened Coulomb potential that evolves self-consistently from a bare potential to the well-known dynamically screened RPA potential for long times. The dependence on the delay time of the differential transmission spectra for a thin layer of GaAs at 15 K is calculated and measured for a 150-fs pump pulse tuned to optical transitions between the light- and heavy-hole valence bands and the conduction band, while a delayed 30-fs probe pulse is tuned to transitions between the spin-orbit split-off valence band to conduction band. The calculated spectra explain the measured ones in a broad range of delay times and for various pump frequencies and intensities qualitatively rather well.