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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.14: Poster

Samstag, 5. März 2005, 11:00–16:30, Poster TU C

Dynamic charge and spin susceptibility of the Hubbard model — •Sebastian Schmitt and Norbert Grewe — Institut für Festkörperphysik, Hochschulstraße 6, 64289 Darmstadt

We present Bethe-Salpeter equations, derived via a cumulant expansion in terms of the transfer between lattice sites, which are valid for models with large local Coulomb matrix elements. Employing a RPA-like decoupling scheme, susceptibilities of a Stoner form are obtained, in which the local parts and their dynamic interactions are explicitly known.

For the Hubbard model the dynamic charge and spin susceptibility is presented and discussed. In particular the spectra of charge and spin fluctuations are analyzed as well as tendencies towards the formation of a charge or magnetically ordered state for various wave vectors, temperatures, and doping.