Regensburg 2022 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 12: Computational Materials Modelling: Physics of Ensembles 1
MM 12.4: Vortrag
Dienstag, 6. September 2022, 11:00–11:15, H44
Self-consistency in GWΓ formalism leading to quasiparticle-quasiparticle couplings — •Carlos Mejuto-Zaera1 and Vojtěch Vlček2 — 1Scoula Internazionale Superiore di Studi Avanzati SISSA, Trieste, Italy — 2University of California Santa Barbara UCSB, USA
Many-body perturbation theory (MBPT) has become a tool of choice for the description of materials. Traditionally tied to the weakly-interacting limit, e.g. through the GW approximation, its expansion towards higher interactions is a fundamental goal in the field. Existing attempts can rely on selected diagram resummation or downfolding, which involve some choice of expansion parameters typically reducing the approach's generality and flexibility. Despite this apparently intrinsic price, MBPT provides through Hedin's equations a formally exact path to describe any dynamically correlated system, regardless of interaction strength. We revisit this framework to disentangle how to systematically extend its practical validity beyond weak interactions, focusing on the structure of the interaction vertex Γ within self-consistent implementations. Using the Hubbard dimer at half-filling, we unveil the role of Γ's functional derivative with respect to the Green's function, hitherto typically neglected, in generating diagrams that can extend the reliability of MBPT towards high interactions [1].
[1] arXiv:2203.05029