Ultra-fast carriers relaxation in bulk silicon following photo-excitation with a short and polarized laser pulse

We use an atomistic approach to provide a novel and ground-breaking interpretation of the ultra-fast carriers relaxation in a realistic material: bulk silicon. By comparing the results of ab initio simulations with recent two-photon photo-emission measurements we show that the description of the carrier relaxation in terms of L. X inter-valley scattering is not correct. The ultra-fast dynamics measured experimentally is, instead, due to the scattering between degenerate L states that is activated by the non-symmetric population of the conduction bands induced by the laser field. This ultra-fast relaxation is, then, entirely due to the specific experimental setup and it can be interpreted by introducing a novel definition of the quasi-particle lifetimes in an out-of-equilibrium context. Copyright (C) EPLA, 2015