Signatures of short-range many-body effects in the dielectric function of silicon for finite momentum transfer.
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.
Weissker
Hans-Christian
HC
Laboratoire des Solides Irradiés UMR 7642, CNRS-CEA/DSM, Ecole Polytechnique, F-91128 Palaiseau, France.
Serrano
Jorge
J
Huotari
Simo
S
Bruneval
Fabien
F
Sottile
Francesco
F
Monaco
Giulio
G
Krisch
Michael
M
Olevano
Valerio
V
Reining
Lucia
L