SKM 2023 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 5: Correlated Electrons: Method Development
TT 5.1: Vortrag
Montag, 27. März 2023, 09:30–09:45, HSZ 204
Generalized Bogoliubov-Hartree-Fock theory for the Hubbard model — •Chris Koschenz1 and Carsten Timm1,2 — 1Institute of Theoretical Physics, TU Dresden, 01062 Dresden, Germany — 2Würzburg-Dresden Cluster of Excellence ct.qmat, TU Dresden, 01062 Dresden, Germany
We present the phase diagram of the Hubbard model on the square lattice up to a four-site unit cell derived via a generalized Bogoliubov-Hartree-Fock theory. Our approach allows to study magnetic ordering, charge ordering, and superconductivity on the same footing and gives additional information about the so-called mixed phases [1]. These phases emerge in parameter ranges where the system is potentially strongly affected by fluctuations and cannot be described by any set of usual Hartree-Fock states (Slater determinants) [1,2]. Furthermore, we show how to obtain the self-consistent set of order parameters by straightforward unrestricted global minimization of the appropriate Landau functional [3]. This method allows us to study the coexistence and competition of various magnetic orders and can be used to study the possibility of additional phase transitions in the coexistence regime. [1] E. Langmann and M. Wallin, J. Stat. Phys. 127, 825 (2007) [2] V. Bach et al., J. Stat. Phys. 76, 3 (1994) [3] R. Agra et al., Eur. J. Phys. 27, 407 (2006)