title: Padé resummation of many-body perturbation theories.
abstract: In a typical scenario the diagrammatic many-body perturbation theory generates asymptotic series. Despite non-convergence, the asymptotic expansions are useful when truncated to a finite number of terms. This is the reason for the popularity of leading-order methods such as the GW approximation in condensed matter, molecular and atomic physics. Appropriate truncation order required for the accurate description of strongly correlated materials is, however, not known a priori. Here an efficient method based on the Padé approximation is introduced for the regularization of perturbative series allowing to perform higher-order self-consistent calculations and to make quantitative predictions on the convergence of many-body perturbation theories. The theory is extended towards excited states where the Wick theorem is not directly applicable. Focusing on the plasmon-assisted photoemission from graphene, we treat diagrammatically electrons coupled to the excited state plasmons and predict new spectral features that can be observed in the time-resolved measurements.
authors.affiliation: Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany. yaroslav.pavlyukh@physik.uni-halle.de.|Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany. yaroslav.pavlyukh@physik.uni-halle.de.
authors.forename: Y
authors.identifier: http://orcid.org/0000-0001-9572-966X
authors.initials: Y
authors.lastname: Pavlyukh