Efficient perturbation theory for quantum lattice models.
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.
Hafermann
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H
I. Institute for Theoretical Physics, University of Hamburg, 20355 Hamburg, Germany.
Li
G
G
Rubtsov
A N
AN
Katsnelson
M I
MI
Lichtenstein
A I
AI
Monien
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H