Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 78: Correlated Electrons: Poster Session

TT 78.36: Poster

Donnerstag, 10. März 2016, 15:00–18:30, Poster D

Mean-field extension of the variational cluster approach — •Jan Lotze and Maria Daghofer — Universität Stuttgart, Institut für Funktionelle Materie und Quantentechnologien, Pfaffenwaldring 57, 70550 Stuttgart

The variational cluster approximation based on a self-energy approach can be used to study correlated-electron Hamiltonians: The self-energy of the system is replaced by that of a 'reference system' that has to have the same interaction, but can have different kinetic energy. In practice, the reference system consists of isolated clusters, which restricts the class of accessible models to those, where the interaction is local, e.g., as in the Hubbard model. Inter-site interactions can be included exactly within each cluster, but not on bonds connecting clusters.

We propose here to use a mean-field decoupling for these bonds. While this is an approximation that falls ouside the self-energy approach, a systematic improvement over simple mean-field treatments becomes possible, as fewer bonds are mean-field decoupled for larger directly solved clusters. We present first results of this extension for the t-J-U model.