Non-local Correlation Effects in Fermionic Many-Body Systems: Overcoming the Non-causality Problem

TL;DR

This paper introduces a causality-preserving extension of local many-body methods like DMFT to include nonlocal correlations, improving the modeling of quasi-2D fermionic systems such as high-temperature superconductors.

Contribution

It proposes a new approach that extends DMFT to nonlocal correlations while maintaining causality, with broad applicability to related many-body techniques.

Findings

Preserves causality in nonlocal correlation calculations

Applicable to cluster, dual boson, and dual fermion methods

Enhances modeling of quasi-2D fermionic systems

Abstract

Motivated by the intriguing physics of quasi-2d fermionic systems, such as high-temperature superconducting oxides, layered transition metal chalcogenides or surface or interface systems, the development of many-body computational methods geared at including both local and non-local electronic correlations has become a rapidly evolving field. It has been realized, however, that the success of such methods can be hampered by the emergence of noncausal features in the effective or observable quantities involved. Here, we present a new approach of extending local many-body techniques such as dynamical mean field theory (DMFT) to nonlocal correlations, which preserves causality and has a physically intuitive interpretation. Our strategy has implications for the general class of DMFT-inspired many-body methods, and can be adapted to cluster, dual boson or dual fermion techniques with minimal effort.