Abstract

The thermalization of nonequilibrium carrier distributions involve fundamentals of thermodynamics and solid-state physics. Femtosecond spectroscopy has been employed to study this process¹ and was analyzed in the framework of Bolzmann kinetics.² However, during and shortly after an ultrashort laser excitation, carrier kinetics are drastically altered. At this early stage the Coulomb potential is still unscreened and there is essentially no energy conservation in two-particle scattering events; instead scattering becomes nonlocal in time. In this regime the evolution of momentum-dependent occupation numbers can only be described by quantum kinetics, including memory structure in the scattering integrals.³

© 1996 Optical Society of America