Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 24: Postersitzung III: Korrelierte Elektronen, ”Orbital Physics”
TT 24.5: Poster
Mittwoch, 10. März 2004, 14:30–19:00, Poster A
Variational cluster approach to extended Hubbard models at half filling — •Markus Aichhorn1, Hans Gerd Evertz1, Wolfgang von der Linden1, and Michael Potthoff2 — 1Institut für Theoretische Physik und Computational Physics, Technische Universität Graz, Petersgasse 16, A-8010 Graz, Austria — 2Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
We present an extension of the recently proposed variational cluster perturbation theory to extended Hubbard models at half filling with repulsive nearest neighbor interaction. The method takes into account short-range correlations exactly by the exact treatment of clusters of finite size via exact diagonalization, whereas long-range order beyond the size of the clusters is treated on a mean-field level. We show that for one dimension results known from Quantum Monte Carlo and Density Matrix Renormalization Group can be reproduced with very good accuracy. Moreover we apply the method to the two-dimensional extended Hubbard model on a square lattice. Different from one dimension, we find a first order phase transition between spin density wave phase and charge density wave phase down to onsite interaction U=3t. In addition, the single-particle spectral function is calculated for both the one-dimensional and the two-dimensional system.