Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 94: Correlated Electrons: Other Theoretical Topics
TT 94.4: Vortrag
Donnerstag, 15. März 2018, 15:45–16:00, H 3010
Divergences of the irreducible vertex functions in correlated metallic systems: Insights from the Anderson Impurity Model — •Patrick Chalupa1, Patrik Gunacker1, Thomas Schäfer1,2,3, Karsten Held1, and Alessandro Toschi1 — 1Institute of Solid State Physics, Technische Universität Wien, 1040 Vienna, Austria — 2Collége de France, 75005 Paris, France — 3Centre de Physique Théorique, École Polytechnique, 91128 Palaiseau, France
We analyze in detail the occurrence of divergences in the irreducible vertex functions of the Anderson impurity model (AIM). These divergences --- a surprising hallmark of the breakdown of many-electron perturbation theory --- have been recently observed in several contexts, including the dynamical mean-field solution of the Hubbard model. Hitherto, however, a clarification of their origin could be obtained only in the limit of high temperatures and large interactions, where the underlying physics is greatly simplified by the absence of low-energy quasiparticle excitations. In this respect, our numerical calculations for the AIM, as well as their comparison with the corresponding results for the Hubbard model, allow us to clarify several open questions about the origin and the properties of vertex divergences occurring in a more interesting context, the correlated metallic regime at low- temperatures. In particular, our analysis (i) rules out a direct correspondence between the vertex divergences and the presence of a Mott metal-insulator transition, (ii) clarifies their relation with the underlying Kondo physics, and, eventually, (iii) individuates which divergences might also appear on the real frequency axis in the limit of zero temperature.