Impact of self-consistency in dual fermion calculations

TL;DR

This paper explores how different self-consistency choices in dual fermion calculations affect physical properties, revealing significant impacts on correlation length, susceptibility, and metallicity in the two-dimensional Hubbard model.

Contribution

It demonstrates the effects of self-consistent impurity selection in dual fermion methods, highlighting differences from traditional DMFT approaches.

Findings

Exponential increase of correlation length and susceptibility at low temperatures.

Pronounced differences between self-consistency schemes.

Self-consistent DF can be more metallic than DMFT.

Abstract

The dual fermion (DF) method allows for calculating corrections due to non-local correlations relative to an effective impurity model. Choosing the impurity as that of a dynamical mean field theory (DMFT) solution at self-consistency is popular, and the corrections from dual fermion theory are physically meaningful. We investigate the effect of choosing the impurity instead in a self-consistent manner and find for the two dimensional Hubbard model an exponentially increase of the correlation length and susceptibility at low temperatures. There are pronounced differences for the two self-consistency schemes that are discussed in the literature; the self-consistent DF solution can even be more metallic than the DMFT solution.