Spectral Functions of the Uniform Electron Gas via Coupled-Cluster Theory and Comparison to the $GW$ and Related Approximations

TL;DR

This paper applies advanced coupled-cluster theory to compute the spectral function of the uniform electron gas, providing insights beyond traditional $GW$ methods and addressing longstanding debates in condensed matter physics.

Contribution

First ab initio coupled-cluster spectral function calculations for the uniform electron gas at $r_s=4$, surpassing $GW$ theory in diagrammatic complexity.

Findings

Coupled-cluster results outperform $GW$ in capturing satellite features.

The study clarifies the occupied bandwidth of metallic sodium.

Results suggest coupled-cluster theory's promising future in condensed matter spectra.

Abstract

We use, for the first time, ab initio coupled-cluster theory to compute the spectral function of the uniform electron gas at a Wigner-Seitz radius of $r_\mathrm{s}=4$. The coupled-cluster approximations we employ go significantly beyond the diagrammatic content of state-of-the-art $GW$ theory. We compare our calculations extensively to $GW$ and $GW$-plus-cumulant theory, illustrating the strengths and weaknesses of these methods in capturing the quasiparticle and satellite features of the electron gas. Our accurate calculations further allow us to address the long-standing debate over the occupied bandwidth of metallic sodium. Our findings indicate that the future application of coupled-cluster theory to condensed phase material spectra is highly promising.