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