Cluster Dual Fermion Approach to Nonlocal Correlations

TL;DR

This paper introduces a cluster Dual Fermion approach that extends cluster DMFT to include nonlocal correlations in crystals, demonstrated by accurate Hubbard model calculations in one dimension.

Contribution

The paper develops a general cluster Dual Fermion framework that captures long-range correlations beyond traditional cluster DMFT, applicable to multiorbital systems.

Findings

The approach reproduces cluster DMFT in the simplest approximation.

The method accurately calculates the Green function of the 1D Hubbard model.

Results agree well with DMRG calculations.

Abstract

We formulate a general cluster Dual Fermion Approach to nonlocal correlations in crystals. The scheme allows the treatment of long-range correlations beyond cluster DMFT and nonlocal effects in realistic calculations of multiorbital systems. We show that the the simplest approximation exactly corresponds to free cluster DMFT. We further consider the relation between the two-particle Green functions in real and dual variables. We apply this approach by calculating the Green function of the Hubbard model in one dimension starting from the two-site cluster DMFT solution. The result agrees well with the Green function obtained from a DMRG calculation.