Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 24: Postersitzung III: Korrelierte Elektronen, ”Orbital Physics”
TT 24.24: Poster
Mittwoch, 10. März 2004, 14:30–19:00, Poster A
Time-dependent Gutzwiller theory of magnetic excitations in the Hubbard model — •Goetz Seibold1, Federico Becca2, and Jose Lorenzana3 — 1Lehrstuhl Theoretische Physik, BTU Cottbus, 03013 Cottbus, Germany — 2SISSA, 34014 Trieste, Italy — 3Dip. di Fisica, Universita di Roma ’La Sapienza’, 00185 Roma, Italy
We use a spin-rotational invariant Gutzwiller energy functional to compute random-phase-approximation-like (RPA) fluctuations on top of the Gutzwiller approximation (GA). Since no restrictions are imposed on the symmetry of the underlying saddle-point solution, our approach is suitable for the evaluation of the magnetic susceptibility and dynamical structure factor in strongly correlated inhomogeneous systems. We present a detailed study of the quality of our approach by comparing with exact diagonalization results and show its much higher accuracy compared to the conventional Hartree-Fock+RPA theory. In infinite dimensions, where the GA becomes exact for the Gutzwiller variational energy, we evaluate ferromagnetic and antiferromagnetic instabilities from the transverse magnetic susceptibility. The resulting phase diagram is in complete agreement with previous variational computations.