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Cumulant Green's function calculations of plasmon satellites in bulk sodium: Influence of screening and the crystal environment

TitleCumulant Green's function calculations of plasmon satellites in bulk sodium: Influence of screening and the crystal environment
Publication TypeJournal Article
Year of Publication2018
AuthorsZhou, J. S., Gatti M., Kas J. J., Rehr J. J., & Reining L.
Abstract

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 quasiparticle 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 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 semicore levels influences the satellites, but not the quasiparticle. Moreover, inclusion of contributions to the screening beyond the random-phase approximation 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 and the retarded 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 1 eV. This stresses the fact that the calculation of satellites is much more delicate than the calculation of a quasiparticle band structure.

JournalPHYSICAL REVIEW B
Volume97
Pagination035137
DOI10.1103/PhysRevB.97.035137
Citation Key ISI:000423115200010