Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 13: Correlated Electrons: Method Development I

TT 13.13: Vortrag

Montag, 9. März 2026, 18:15–18:30, HSZ/0101

Nagaoka kinetic ferromagnetism 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

We present a study of the infinite-U Hubbard model using an extension of the functional renormalization group (FRG) that works directly with non-canonical fermionic operators. Thus the projected Hilbert space is incorporated exactly, yielding an unbiased diagrammatic method that works in the thermodynamic limit, suitable to capture the long range physics of the strongly correlated electrons. We discuss the magnetic phase diagram for the full range of hole doping. Upon increasing the density, we identify a paramagnetic ground-state, followed by an antiferromagnetic stripe order and finally Nangaoka's kinetic ferromagnetism at high densities. The dynamical susceptibilities reveal the evolution of a paramagnon band into a diffusive continuum with increasing electron density.

Keywords: functional renormalization group; Nagaoka ferromagnetism; Hubbard model; t-J model; strong correlation