Dresden 2017 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 5: Correlated Electrons: (General) Theory 1

TT 5.3: Talk

Monday, March 20, 2017, 10:00–10:15, HSZ 304

Breakdown of the many-body perturbation theory: Vertex divergences in the Anderson Impurity Model — •Patrick Chalupa, Patrik Gunacker, Thomas Schäfer, Karsten Held, and Alessandro Toschi — Technische Universität Wien, Karlsplatz 13, 1040 Wien

The recently discovered [1,2] occurrence of multiple divergences in the irreducible vertex functions of strongly correlated electron models, poses serious problems to the state-of-the-art many-body theory. Dynamical mean-field theory calculations for the Hubbard model have shown several lines of divergences, surrounding the Mott-Hubbard metal-insulator transition, a clear hint of a highly non-perturbative origin. At high temperatures/large U, where the Hubbard model approaches the atomic limit, the divergences could be ascribed to a unique underlying energy scale ν^*. This simple picture is however not applicable in the most interesting parameter regime of low temperatures and intermediate U.

For this reason we analysed a simpler model where a similar physics could be realized: the Anderson impurity model. This provides a more feasible way to treat quasiparticle physics in the parameter regime of interest. Our CT-HYB calculations, performed with w2dynamics [3] at the two particle level, extending to even lower temperatures than before, provide novel insight into this topic.

[1] T.Schäfer, et al., 1606.03393, to be published in Phys. Rev. B

[2] T.Schäfer, et al., Phys. Rev. Lett. 110, 246405 (2013)

[3] N.Parragh, et al., Phys. Rev. B 86, 155158 (2012)