Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 13: Correlated Electrons: Method Development I

TT 13.12: Talk

Monday, March 9, 2026, 18:00–18:15, HSZ/0101

Strong-coupling functional renormalization group: non-Fermi liquid physics in the infinite-U Hubbard model — Jonas Arnold, Peter Kopietz, and •Andreas Rückriegel — Institut für Theoretische Physik, Universität Frankfurt, Max-von-Laue Straße 1, 60438 Frankfurt, Germany

Exact functional renormalization group (FRG) flow equations for quantum systems can be derived directly within an operator formalism without using functional integrals. This simple insight allows us to apply unbiased FRG methods directly to strongly correlated electron systems with projected Hilbert spaces. Here, we use this approach to compute the electronic spectral function of the Hubbard model at infinite on-site repulsion where many-body states involving doubly occupied lattice sites are eliminated from the physical Hilbert space. For a square lattice with nearest-neighbor hopping we find that the finite-temperature electronic spectrum evolves from a Fermi liquid at low densities to an incoherent non-Fermi liquid at larger densities. Both at high and low densities, the volume of the Fermi surface is not constrained by Luttinger's theorem.

Keywords: Functional renormalization group; Hubbard model; strong correlations; non-Fermi liquid; t-J model