Spectral properties of quasiparticles in a semiconductor

The one-electron excitation spectrum of the prototype semiconductor Si has been obtained from a first-principles calculation of the spectral-weight function A(q→,ω) of the interacting one-electron Green's function. The Dyson equation has been solved with the self-energy operator obtained in the GW approximation, where the bare propagator G and the {ω}-dependent screening matrix $W,$ without (random-phase approximation) and with (time-dependent local density approximation) vertex corrections, have been computed within Kohn-Sham--local-density-approximation theory. Positions of quasiparticle peaks (i.e., the ``band structure''), their lifetimes, and satellite (plasmaron) spectral structures are extracted in a broad energy range.