Second-order dual fermion for multi-orbital systems

TL;DR

This paper extends the dual fermion method to multi-orbital systems, enabling the study of non-local correlations beyond single-orbital models, and applies it to SrVO3 with benchmarking on small systems.

Contribution

The authors develop and implement a second-order dual fermion approach for multi-orbital systems, broadening the applicability of the method beyond single-orbital models.

Findings

Successfully applied to SrVO3 to analyze spatial correlations.

Benchmarked the method on exactly solvable small systems.

Demonstrated the method's effectiveness in capturing non-local correlations.

Abstract

In dynamical mean-field theory, the correlations between electrons are assumed to be purely local. The dual fermion approach provides a systematic way of adding non-local corrections to the dynamical mean-field theory starting point. Initial applications of this method were largely restricted to the single-orbital Hubbard model. Here, we present an implementation of second-order dual fermion for general multi-orbital systems and use this approach to investigate spatial correlations in SrVO$_3$. In addition, the approach is benchmarked in several exactly solvable small systems.