title: Efficient perturbation theory for quantum lattice models.
abstract: We present a novel approach to long-range correlations beyond dynamical mean-field theory, through a ladder approximation to dual fermions. The new technique is applied to the two-dimensional Hubbard model. We demonstrate that the transformed perturbation series for the nonlocal dual fermions has superior convergence properties over standard diagrammatic techniques. The critical Néel temperature of the mean-field solution is suppressed in the ladder approximation, in accordance with quantum Monte Carlo results. An illustration of how the approach captures and allows us to distinguish short- and long-range correlations is given.
authors.affiliation: I. Institute for Theoretical Physics, University of Hamburg, 20355 Hamburg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Hafermann
authors.forename: G
authors.initials: G
authors.lastname: Li
authors.forename: A N
authors.initials: AN
authors.lastname: Rubtsov
authors.forename: M I
authors.initials: MI
authors.lastname: Katsnelson
authors.forename: A I
authors.initials: AI
authors.lastname: Lichtenstein
authors.forename: H
authors.initials: H
authors.lastname: Monien