# Effect of non-local correlations on the electronic structure of LiFeAs

## TL;DR

This study demonstrates that non-local electronic correlations are crucial for accurately describing the spectral properties and Fermi surface of LiFeAs, highlighting the limitations of local approximations like DMFT.

## Contribution

The paper introduces a multi-orbital TPSC approach to explicitly account for non-local correlations in LiFeAs, providing a more accurate theoretical description compared to local methods.

## Key findings

- Non-local correlations significantly influence spectral functions and Fermi surface features.
- The TPSC approach captures experimental ARPES and dHvA data better than DMFT.
- Non-local correlations are essential for understanding iron-based superconductor properties.

## Abstract

We investigate the role of non-local correlations in LiFeAs by exploring an ab-initio-derived multi-orbital Hubbard model for LiFeAs via the Two-Particle Self-Consistent (TPSC) approach. The multi-orbital formulation of TPSC approximates the irreducible interaction vertex to be an orbital-dependent constant, which is self-consistently determined from local spin and charge sum rules. Within this approach, we disentangle the contribution of local and non-local correlations in LiFeAs and show that in the local approximation one recovers the dynamical-mean field theory (DMFT) result. The comparison of our theoretical results to most recent angular-resolved photoemission spectroscopy (ARPES) and de-Haas van Alphen (dHvA) data shows that non-local correlations in LiFeAs are decisive to describe the measured spectral function $A(\vec k,\omega)$, Fermi surface and scattering rates. These findings underline the importance of non-local correlations and benchmark different theoretical approaches for iron-based superconductors.