体相钠等离子体子卫星的累积格林函数计算：屏蔽和晶体环境的影响
Cumulant Green's function calculations of plasmon satellites in bulk sodium: influence of screening and the crystal environment
摘要：
我们提出了从头计算的光电子能谱散装钠使用不同口味的累积展开近似的格林函数。特别是，我们研究了等离子体卫星的色散和强度。我们发现，卫星光谱比准粒子（QP）光谱，这表明，卫星的实验研究可以产生额外的信息超出了通常的研究的能带结构的许多细节更敏感。特别是，与均匀电子气（HEG）的比较表明，卫星受到晶体环境的影响，尽管钠的晶体势很弱。此外，晶格常数的温度依赖性反映在卫星的位置上。筛选的细节也起着重要的作用;特别是，从2s和2 p半芯能级跃迁的贡献影响卫星，但不影响QP。此外，将对筛选的贡献包括在RPA之外对卫星也有影响。最后，我们阐明了电子和空穴耦合的重要性，通过比较的时间顺序（TOC）和延迟（RC）累积展开近似的结果。我们再次发现了微小但明显的差异。由于所有的小影响加起来，我们最先进的计算产生一个卫星的位置，这是改善相对于以前的计算几乎一个电子伏特。这强调了这样一个事实，即卫星的计算比QP能带结构的计算精细得多。
英文摘要：
We present ab initio calculations of the photoemission spectra of bulk sodium using different flavors of the cumulant expansion approximation for the Green's function. In particular, we study the dispersion and intensity of the plasmon satellites. We show that the satellite spectrum is much more sensitive to many details than the quasi-particle (QP) spectrum, which suggests that the experimental investigation of satellites could yield additional information beyond the usual studies of the band structure. In particular, a comparison to the homogeneous electron gas (HEG) shows that the satellites are influenced by the crystal environment, although the crystal potential in sodium is weak. Moreover, the temperature dependence of the lattice constant is reflected in the position of the satellites. Details of the screening also play an important role; in particular, the contribution of transitions from 2s and 2p semi-core levels influence the satellites, but not the QP. Moreover, inclusion of contributions to the screening beyond the RPA has an effect on the satellites. Finally, we elucidate the importance of the coupling of electrons and holes by comparing the results of the time-ordered (TOC) and the retarded (RC) cumulant expansion approximations. Again, we find small but noticeable differences. Since all the small effects add up, our most advanced calculation yields a satellite position which is improved with respect to previous calculations by almost one eV. This stresses the fact that the calculation of satellites is much more delicate than the calculation of a QP band structure.
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