Many-body perturbation theory and non-perturbative approaches: screened interaction as the key ingredient. (2nd March 2018)

• Record Type: Journal Article
• Authors: Tarantino, Walter; Mendoza, Bernardo S; Romaniello, Pina; Berger, J A; Reining, Lucia
• Is Part Of: Journal of physics. Volume 30:Number 13(2018)
• Publication Date: 2018-03-02
• Subjects: Green's functions -- many-body perturbation theory -- Kadanoff–Baym equation -- one-point model -- GW -- RPA; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/1361-648X/aaaeab
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: Many-body perturbation theory is often formulated in terms of an expansion in the dressed instead of the bare Green's function, and in the screened instead of the bare Coulomb interaction. However, screening can be calculated on different levels of approximation, and it is important to define what is the most appropriate choice. We explore this question by studying a zero-dimensional model (so called 'one-point model') that retains the structure of the full equations. We study both linear and non-linear response approximations to the screening. We find that an expansion in terms of the screening in the random phase approximation is the most promising way for an application in real systems. Moreover, by making use of the nonperturbative features of the Kadanoff–Baym equation for the one-body Green's function, we obtain an approximate solution in our model that is very promising, although its applicability to real systems has still to be explored.