# Diagrammatic routes to nonlocal correlations beyond dynamical mean field theory

## TL;DR

This paper reviews diagrammatic methods that extend dynamical mean field theory to include nonlocal correlations, enabling the study of long-range fluctuations and critical phenomena in strongly correlated electron systems.

## Contribution

It introduces diagrammatic extensions of DMFT using local two-particle vertices to incorporate nonlocal correlations beyond local approximations.

## Key findings

- Successfully addresses long-range charge, magnetic, and superconducting fluctuations.
- Enables analysis of quantum criticality in strongly correlated systems.
- Provides a framework for realistic material calculations.

## Abstract

Strong electronic correlations pose one of the biggest challenges to solid state theory. We review recently developed methods that address this problem by starting with the local, eminently important correlations of dynamical mean field theory (DMFT). On top of this, non-local correlations on all length scales are generated through Feynman diagrams, with a local two-particle vertex instead of the bare Coulomb interaction as a building block. With these diagrammatic extensions of DMFT long-range charge-, magnetic-, and superconducting fluctuations as well as (quantum) criticality can be addressed in strongly correlated electron systems. We provide an overview of the successes and results achieved---hitherto mainly for model Hamiltonians---and outline future prospects for realistic material calculations.