SUBPICOSECOND PLASMON RESPONSE - BUILDUP OF SCREENING

The screened Coulomb Keldysh propagator is evaluated in the time-domai n for ultra-short-pulse laser excitation of a semiconductor using the nonequilibrium Green-function technique. The buildup of screening in t he time interval during and shortly after the pulse excitation is trea ted. A time-dependent plasmon-pole approximation is derived and shown to give an excellent description of the dynamics of screening after a resonant femtosecond