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TT: Fachverband Tiefe Temperaturen

TT 45: Correlated Electrons: Poster Session

TT 45.107: Poster

Thursday, March 29, 2012, 15:00–19:00, Poster B

Variational cluster approach for strongly correlated bosonic systems in and out of equilibrium — •Enrico Arrigoni, Benjamin Kollmitzer, Michael Knap, and Wolfgang von der Linden — Institute of Theoretical and Computational Physics, Graz University of Technology, 8010 Graz, Austria

We present a variational cluster approach to treat strongly-correlated lattice bosons in the superfluid phase. To this end, we reformulate the method within a pseudoparticle formalism, whereby cluster excited states are described in terms of particle-like excitations. The approximation amounts to solving a multi-component noninteracting bosonic system by means of a multi-mode Bogoliubov transformation. A criterion for the stability of the solution is discussed.

For the two-dimensional Bose-Hubbard model the method provides excellent agreement with Quantum Monte Carlo results even in the vicinity of the tip of the Mott lobe, both on the insulating as well as in the superfluid phase.

We illustrate the application of the method to strongly-correlated bosonic systems out of equilibrium within a Keldysh Green’s function formulation.