Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 24: Correlated Electrons: (General) Theory 2

TT 24.3: Vortrag

Mittwoch, 25. März 2009, 10:00–10:15, HSZ 301

Long-range correlations beyond DMFT: the ladder dual fermion approach — •Hartmut Hafermann^1,3, Alexei N. Rubtsov², Mikhail I. Katsnelson³, and Alexander I. Lichtenstein¹ — ¹I. Institute for Theoretical Physics, University of Hamburg, 20355 Hamburg, Germany — ²Department of Physics, Moscow State University, 119992 Moscow, Russia — ³Institute for Molecules and Materials, Radboud University of Nijmegen, 6525 ED Nijmegen, The Netherlands

The dual fermion approach is a systematic perturbative extension of dynamical mean-field theory to describe the physics of strongly correlated lattice fermions. We generalize the approach to include long-range correlations via a ladder approximation to the self-energy. The method is applied to the two-dimensional Hubbard model. While the mean-field solution fails to describe the physics in the vicinity of the antiferromagnetic instability, the ladder approximation recovers good agreement to quantum Monte-Carlo results. Inclusion of the long-range correlations leads to the formation of a pseudogap in the local density of states.