Screened extended Koopmans' theorem: photoemission at weak and strong correlation

TL;DR

This paper introduces a screened extended Koopmans' theorem that accurately predicts band gap opening in both weakly and strongly correlated materials, advancing ab-initio electronic structure calculations.

Contribution

The method incorporates electron screening into the extended Koopmans' theorem, enabling a unified description of photoemission spectra across different correlation regimes.

Findings

Successfully applied to LiH, Si, and NiO

Correctly predicts band gap opening in various systems

Marks progress towards unified photoemission modeling

Abstract

By introducing electron screening in the extended Koopmans' theorem we correctly describe the band gap opening in weakly as well as strongly correlated systems. We show this by applying our method to bulk LiH, Si, and paramagnetic as well as antiferromagnetic NiO. Although incorrect features remain in the full photoemission spectra, this is a remarkable result for an ab-initio electronic structure method and it opens the way to a unified description of photoemission spectra at weak and strong correlation.