期刊
PHYSICAL REVIEW B
卷 83, 期 13, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.83.134507
关键词
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资金
- Austrian Science Fund (FWF) [W1208-N18, P18551-N16]
- Austrian Science Fund (FWF) [P18551] Funding Source: Austrian Science Fund (FWF)
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.
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