title: Signatures of short-range many-body effects in the dielectric function of silicon for finite momentum transfer.
abstract: We present an investigation of the dynamic structure factor and of the dielectric function epsilonM(Q,omega) of the prototypical semiconductor silicon for finite momentum transfer, combining inelastic x-ray scattering experiments and ab initio calculations. In contrast with optical spectra, for finite momentum transfer time-dependent density-functional theory in the adiabatic local-density approximation together with lifetime broadening describes the physics of valence excitations correctly. Major structures in the spectra, governed by short-range crystal and exchange-correlation local-field effects, are strongly influenced by a mixing of transitions of positive and negative energies, in striking difference to spectra for vanishing momentum transfer. This mixing gives rise to a pronounced Fano asymmetry.
authors.affiliation: Laboratoire des Solides Irradiés UMR 7642, CNRS-CEA/DSM, Ecole Polytechnique, F-91128 Palaiseau, France.
authors.forename: Hans-Christian
authors.initials: HC
authors.lastname: Weissker
authors.forename: Jorge
authors.initials: J
authors.lastname: Serrano
authors.forename: Simo
authors.initials: S
authors.lastname: Huotari
authors.forename: Fabien
authors.initials: F
authors.lastname: Bruneval
authors.forename: Francesco
authors.initials: F
authors.lastname: Sottile
authors.forename: Giulio
authors.initials: G
authors.lastname: Monaco
authors.forename: Michael
authors.initials: M
authors.lastname: Krisch
authors.forename: Valerio
authors.initials: V
authors.lastname: Olevano
authors.forename: Lucia
authors.initials: L
authors.lastname: Reining