Regensburg 2010 – wissenschaftliches Programm
TT 24.5: Vortrag
Mittwoch, 24. März 2010, 15:00–15:15, H19
Importance of local correlations for the order parameter of high-Tc superconductors — •Matthias Balzer and Michael Potthoff — I. Institut für Theoretische Physik, Universität Hamburg, Germany
Using an extension of the variational cluster approximation (VCA), the relevance of bath degrees of freedom in a cluster-embedding approach for the size of the d-wave superconducting order parameter is studied within the hole- and electron-doped two-dimensional Hubbard model at zero temperature. We discuss results obtained for a reference system consisting of a plaquette of four correlated and four bath sites in addition and compare with results obtained via VCA for the plain plaquette without bath sites on the one hand and with results from previous cellular (plaquette) dynamical mean-field calculations on the other. It is shown that local, i.e. temporal, correlations are essential: Including a single bath degree of freedom considerably decreases the order parameter and provides a substantial gain of binding energy. Bath sites are also seen to partially compensate for the artificial breaking of translational symmetry introduced by the real-space quantum cluster approach.