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Functional renormalization group (fRG) methods relate theories at different energy scales via an exact flow equation for a functional of the fields. In this talk, I will focus on a one-particle irreducible, purely fermionic formulation and, in particular, on its application to phases of broken symmetries and multiband Hubbard models. First, I will report on a recent fRG study on antiferromagnetic ordering in a simple two-pocket model, including a possible extension to coexistence phases of antiferromagnetism and superconductivity. The second part will be devoted to multiband systems. Particularities of the point-group behavior of multiband Hubbard models are discussed and fRG results are presented for a generic three-band model for the cuprate superconductors. Finally, an outlook on a potentially highly parallelizable fRG algorithm is given, which should be suitable for calculations with a larger number of bands.

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Stefan Meier
Seminar room 03, ETP
Contact: not specified