Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 31: Low-dimensional Systems - Models I
TT 31.6: Vortrag
Donnerstag, 29. März 2007, 19:00–19:15, H19
Cluster approach to magnetic excitations in high-Tc superconductors — •Sascha Brehm1, Enrico Arrigoni2, Michael Potthoff1, Markus Aichhorn1, and Werner Hanke1 — 1Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany — 2Institut für Theoretische Physik, Technische Universität Graz, Petersgasse 16, A-8010 Graz, Austria
A new scheme is presented for calculating two-particle spin and charge response functions within symmetry-broken, e.g. antiferromagnetic (AF) and d-wave superconducting (dSC), phases. The scheme is based on the variational cluster approach (VCA). Normal and anomalous one-particle Green’s functions of the two-dimensional Hubbard model in the thermodynamical limit are obtained from variationally optimized self-energies of finite clusters with up to 10 sites. At zero temperature, a band Lanczos algorithm is used for the cluster diagonalization. Analogous to the one-particle level, the magnetic and charge susceptibilities are then derived from the frequency-dependent two-particle vertex of the isolated cluster. Results are presented for the AF half-filled case, for the underdoped system with microscopically coexisting AF and dSC order as well as for the paramagnetic dSC phase at optimal doping. Characteristic features of the filling-dependent magnetic excitation spectrum (collective modes as well as continuum) are worked out for normal state and AF/dSC symmetry-broken phases.