Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 28: Correlated Electrons: General Theory

TT 28.8: Vortrag

Donnerstag, 30. März 2006, 12:00–12:15, HSZ 301

Static vs. Dynamical Mean Field Theory of Mott Antiferromagnets — •Giorgio Sangiovanni¹, Alessandro Toschi¹, Erik Koch², Karsten Held¹, Massimo Capone^3,4, Claudio Castellani⁴, and Olle Gunnarsson¹ — ¹Max-Planck Institut für Festkörperforschung, Stuttgart — ²Institut für Festkörperforschung, Forschungszentrum, Jülich — ³Istituto dei Sistemi Complessi del CNR, Rom — ⁴Dipartimento di Fisica Università di Roma "La Sapienza", Rom

In recent years, our ability to calculate strongly correlated materials has substantially improved. For instance, local density approximation supplemented by a local Coulomb interaction U treated in the static Hartree-Fock (HF) mean field theory (LDA+U), gives extremely accurate results for ground-state properties at large U, especially in the presence of magnetic or orbital ordering. On the other hand, dynamic properties are not well described by LDA+U, due to the too poor treatment of excited states given by HF. To go beyond this approximation, the more sophisticated LDA+DMFT has been recently developed. Considering the antiferromagnetic phase of a simple model, the single-band Hubbard model, we explicitely analyze the differences between static and dynamical mean field theory. In DMFT the HF band is strongly renormalized and spectral weight is trasferred to spin-polaron side bands. Already for intermediate U the overall bandwidth is larger than in HF and the gap is considerably smaller. Such differences survive any renormalization of U. We compare our results with photoemission experiments for Cr-doped V₂ O₃ obtaining extremely good qualitative agreement.