Weissker Hans-Christian, Serrano Jorge, Huotari Simo, Bruneval Fabien, Sottile Francesco, Monaco Giulio, Krisch Michael, Olevano Valerio, Reining Lucia
Laboratoire des Solides Irradiés UMR 7642, CNRS-CEA/DSM, Ecole Polytechnique, F-91128 Palaiseau, France.
Phys Rev Lett. 2006 Dec 8;97(23):237602. doi: 10.1103/PhysRevLett.97.237602. Epub 2006 Dec 4.
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.
我们结合非弹性X射线散射实验和从头算计算，对典型半导体硅在有限动量转移下的动态结构因子和介电函数εM(Q,ω)进行了研究。与光谱不同，对于有限动量转移，绝热局域密度近似下的含时密度泛函理论加上寿命展宽能正确描述价激发的物理过程。光谱中的主要结构受短程晶体和交换关联局域场效应支配，正能和负能跃迁的混合对其有强烈影响，这与零动量转移时的光谱形成显著差异。这种混合导致了明显的法诺不对称性。
