2016/01/17 by Y. Pavlyukh, Pavlyukh, Yaroslav, Jamal Berakdar +2
Physics and Astronomy · #Advanced Chemical Physics Studies #Atomic and Molecular Physics #Cold Atom Physics and Bose-Einstein Condensates #FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el)
paper · pdf · doi:10.48550/arxiv.1601.04285
openalex publication_date 2016/01/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 popularity of leading-order methods such as GW approximation in condensed matter, molecular and atomic physics. Emerging higher-order implementations suffer from the appearance of nonsimple poles in the frequency-dependent Green's functions and negative spectral densities making self-consistent determination of the electronic structure impossible. Here a method based on the Padé approximation for overcomming these difficulties is proposed and applied to the Hamiltonian describing a core electron coupled to a single plasmonic excitation. By solving the model purely diagrammatically, expressing the self-energy in terms of combinatorics of chord diagrams, and regularizing the diverging perturbative expansions using the Padé approximation the spectral function is determined self-consistently using 3111 diagrams up to the sixth order.