Variational cluster approach for strongly correlated lattice bosons in the superfluid phase

Michael Knap, Enrico Arrigoni, Wolfgang Von Der Linden

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Abstract

We extend the variational cluster approach to deal with strongly correlated lattice bosons in the superfluid phase. To this end, we reformulate the approach within a pseudoparticle formalism, whereby cluster excitations are described by particlelike excitations. The approximation amounts to solving a multicomponent noninteracting bosonic system by means of a multimode Bogoliubov approximation. A source-and-drain term is introduced in order to break U(1) symmetry at the cluster level. We provide an expression for the grand potential, the single-particle normal and anomalous Green's functions, the condensate density, and other static quantities. As a first nontrivial application of the method we choose the two-dimensional Bose-Hubbard model and evaluate results in both the Mott and the superfluid phases. Our results show an excellent agreement with quantum Monte Carlo calculations.

Original languageEnglish
Article number134507
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume83
Issue number13
DOIs
StatePublished - 7 Apr 2011
Externally publishedYes

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