Excitonic and quasiparticle lifetime effects on silicon electron energy loss spectra from first principles -: art. no. 035308

The quasiparticle decays due to electron-electron interaction in silicon are studied by means of first-principles all-electron GW approximation. The spectral function as well as the dominant relaxation mechanisms giving rise to the finite lifetime of quasiparticles are analyzed. It is then shown that these lifetimes and the quasiparticle energies can be used to compute the complex dielectric function including many-body effects without resorting to empirical broadening to mimic the decay of excited states. This method is applied for the computation of the electron energy loss spectrum of silicon. The location and line shape of the plasmon peak are discussed in detail.