title: Dynamical effects in electron spectroscopy.
abstract: 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.
authors.affiliation: Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM-IRAMIS, Université Paris-Saclay, F-91128 Palaiseau, France.
authors.forename: Jianqiang Sky
authors.initials: JS
authors.lastname: Zhou
authors.affiliation: European Theoretical Spectroscopy Facility (ETSF).
authors.forename: J J
authors.initials: JJ
authors.lastname: Kas
authors.affiliation: Department of Physics, King's College London, London WC2R 2LS, United Kingdom.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Sponza
authors.affiliation: Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM-IRAMIS, Université Paris-Saclay, F-91128 Palaiseau, France.
authors.forename: Igor
authors.initials: I
authors.lastname: Reshetnyak
authors.affiliation: Institut für Physik und IRIS Adlershof, Humboldt-Universität zu Berlin, D-12489 Berlin, Germany.
authors.forename: Matteo
authors.initials: M
authors.lastname: Guzzo
authors.affiliation: Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM-IRAMIS, Université Paris-Saclay, F-91128 Palaiseau, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Giorgetti
authors.affiliation: Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM-IRAMIS, Université Paris-Saclay, F-91128 Palaiseau, France.
authors.forename: Matteo
authors.initials: M
authors.lastname: Gatti
authors.affiliation: Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM-IRAMIS, Université Paris-Saclay, F-91128 Palaiseau, France.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sottile
authors.affiliation: European Theoretical Spectroscopy Facility (ETSF).
authors.forename: J J
authors.initials: JJ
authors.lastname: Rehr
authors.affiliation: Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM-IRAMIS, Université Paris-Saclay, F-91128 Palaiseau, France.
authors.forename: Lucia
authors.initials: L
authors.lastname: Reining