Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 7: Matter at Low Temperature: Poster Session

TT 7.15: Poster

Monday, February 25, 2008, 14:00–18:00, Poster B

Bosonic Dynamical Mean-Field Theory — •Krzysztof Byczuk and Dieter Vollhardt — Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute for Physics, University of Augsburg, D-86135 Augsburg, Germany

We present the first comprehensive, thermodynamically consistent theory of correlated lattice boson systems, namely a bosonic dynamical mean-field theory (B-DMFT), which is applicable for arbitrary values of the coupling parameters and temperatures [1]. B-DMFT includes all local, dynamical correlations of the many-boson system and becomes exact in the limit of infinite space dimensions in analogy with its successful fermionic counterpart. In contrast to previously formulated mean-field theories for bosons it treats normal and condensed bosons on equal footing and is thus able to describe their dynamical coupling. We discuss in detail various limits of B-DMFT where exact and well-known approximate results are recovered. In particular we elucidate the relation between B-DMFT and the static mean-field theories of Bogoliubov and that of Fisher et al. [2]. A lattice model of itinerant and localized, interacting bosons ("Bosonic Falicov-Kimball model") is solved explicitly within B-DMFT. The local correlations are found to enhance both the BEC transition temperature and the condensate fraction relative to the non-interacting system.

[1] K. Byczuk and D. Vollhardt, arXiv:0706.0839

[2] M.P. Fisher, P.B. Weichman, G.Grinstein, and D.S. Fisher, Phys. Rev. B 40, 546 (1989).