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Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 91: Correlated Electrons: Method Development

TT 91.2: Vortrag

Donnerstag, 15. März 2018, 15:15–15:30, H 0104

Full frequency and momentum parametrization of the two-particle vertex in functional RG for fermionic lattice models — •Cornelia Hille1, Agnese Tagliavini1,2, Alessandro Toschi2, Sabine Andergassen1, and Carsten Honerkamp31Universität Tübingen, Tübingen, Deutschland — 2Technische Universität Wien, Wien, Österreich — 3RWTH Aachen, Aachen, Deutschland

The functional renormalization group (fRG) provides an unbiased method to investigate competing instabilities in fermionic lattice models. So far fRG applications succeeded in describing the qualitative phase diagrams for the perturbative coupling regime of various classes of one-band and multi-band models. However, quantitative predictions, e.g. about energy scales or susceptibilities, were not truly controlled because the full parameter dependence of the two-particle vertex had to be simplified for the sake of numerical feasibility, mostly by disregarding the frequency dependence of the vertex which rendered the selfenergy hard to include. Here we show how combining the vertex parametrization guided by the high frequency asymptotics and the expansion of the momentum dependences in terms of form factors results in a significant improvement of the implementation. By including the selfenergy and the susceptibility flow, we can directly compute physical observables that stand the comparison with other methods. With our unbiased implementation, we can systematically investigate the corrections to previous fRG approximations in the 2D-Hubbard model.

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