Ab-initio self-energy corrections in systems with metallic screening

TL;DR

This paper introduces a computationally efficient method to include intraband contributions in self-energy calculations for metals, preventing spurious gaps and improving accuracy in electronic structure predictions.

Contribution

A new, stable, and inexpensive fitting approach for the polarizability's small-q expansion, enhancing GW calculations for metallic systems.

Findings

Accurately reproduces intraband effects in homogeneous electron gas

Prevents spurious gaps at the Fermi energy in real metals

Demonstrates computational efficiency over existing methods

Abstract

The calculation of self-energy corrections to the electron bands of a metal requires the evaluation of the intraband contribution to the polarizability in the small-q limit. When neglected, as in standard GW codes for semiconductors and insulators, a spurious gap opens at the Fermi energy. Systematic methods to include intraband contributions to the polarizability exist, but require a computationally intensive Fermi-surface integration. We propose a numerically cheap and stable method, based on a fit of the power expansion of the polarizability in the small-q region. We test it on the homogeneous electron gas and on real metals such as sodium and aluminum.