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TT: Fachverband Tiefe Temperaturen
TT 13: Correlated Electrons: Method Development I
TT 13.9: Talk
Monday, March 9, 2026, 17:15–17:30, HSZ/0101
Fluctuating field theory description of collective instabilities in the doped Hubbard model — •Erik Linnér1,2, Laura Torchia1, Silke Biermann2,3,4, and Massimo Capone1,5 — 1International School for Advanced Studies (SISSA), Trieste, Italy — 2CPHT, CNRS, École Polytechnique, Institut Polytechnique de Paris, Palaiseau, France — 3Collège de France, Paris, France — 4European Theoretical Spectroscopy Facility, Palaiseau, France — 5CNR-IOM, Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, Trieste, Italy
Fluctuating field theory is a recently developed method for the description of competing collective fluctuations in correlated electron systems, able to account for spin, charge, and superconducting instabilities. On the basis of a variational principle, the method allows to explicitly account for the leading collective modes and their interplay, with access to electronic and spectroscopic properties. Extending its prior application to the Hubbard model at half-filling, we investigate its description of the doped Hubbard model, accounting for various spin instabilities. Interestingly, unlike for Néel ordering which dominates near half-filling, we show that the phase structure of the fluctuating fields for collective instabilities with arbitrary ordering vector Q become important. Within the method, the incommensurate spin ordering driven by doping is associated with a phase structure expressing the modulation of the ordering relative the underlying lattice geometry. Thus, we observe the method, despite its weak-coupling rot, gives an efficient tool to investigate the phase diagram beyond mean-field theory.
Keywords: Magnetism; Incommensurate; Hubbard model; Doping; Phase diagram