Zhou Jianqiang Sky, Kas J J, Sponza Lorenzo, Reshetnyak Igor, Guzzo Matteo, Giorgetti Christine, Gatti Matteo, Sottile Francesco, Rehr J J, Reining Lucia
Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM-IRAMIS, Université Paris-Saclay, F-91128 Palaiseau, France.
European Theoretical Spectroscopy Facility (ETSF).
J Chem Phys. 2015 Nov 14;143(18):184109. doi: 10.1063/1.4934965.
One of the big challenges of theoretical condensed-matter physics is the description, understanding, and prediction of the effects of the Coulomb interaction on materials properties. In electronic spectra, the Coulomb interaction causes a renormalization of energies and change of spectral weight. Most importantly, it can lead to new structures, often called satellites. These can be linked to the coupling of excitations, also termed dynamical effects. State-of-the-art methods in the framework of many-body perturbation theory, in particular, the widely used GW approximation, often fail to describe satellite spectra. Instead, approaches based on a picture of electron-boson coupling such as the cumulant expansion are promising for the description of plasmon satellites. In this work, we give a unified derivation of the GW approximation and the cumulant expansion for the one-body Green's function. Using the example of bulk sodium, we compare the resulting spectral functions both in the valence and in the core region, and we discuss the dispersion of quasi-particles and satellites. We show that self-consistency is crucial to obtain meaningful results, in particular, at large binding energies. Very good agreement with experiment is obtained when the intrinsic spectral function is corrected for extrinsic and interference effects. Finally, we sketch how one can approach the problem in the case of the two-body Green's function, and we discuss the cancellation of various dynamical effects that occur in that case.
理论凝聚态物理的一大挑战是描述、理解和预测库仑相互作用对材料性质的影响。在电子光谱中，库仑相互作用导致能量重整化和光谱权重变化。最重要的是，它可导致新结构，通常称为卫星峰。这些卫星峰可与激发耦合相关联，也称为动力学效应。多体微扰理论框架下的先进方法，特别是广泛使用的GW近似，常常无法描述卫星光谱。相反，基于电子-玻色子耦合图像的方法，如累积量展开，对于描述等离子体卫星峰很有前景。在这项工作中，我们对单粒子格林函数的GW近似和累积量展开进行了统一推导。以体相钠为例，我们比较了价带和芯区的所得光谱函数，并讨论了准粒子和卫星峰的色散。我们表明自洽性对于获得有意义的结果至关重要，特别是在大结合能情况下。当对本征光谱函数进行外在和干涉效应校正时，与实验结果取得了很好的一致性。最后，我们简述了在双粒子格林函数情形下如何处理该问题，并讨论了在那种情况下出现的各种动力学效应的抵消。
