Conserving quasiparticle calculations for small metal clusters

TL;DR

This paper introduces a new GW-based method for calculating quasiparticle properties in finite systems, directly deriving the screened interaction from linear response, ensuring conservation laws are satisfied.

Contribution

The paper presents a novel GW calculation approach that directly uses linear response for the screened interaction, improving conservation properties in quasiparticle calculations.

Findings

Accurate energy renormalizations for Na clusters

Level broadenings match experimental trends

Improved conserving approximations over RPA-level results

Abstract

A novel approach for GW-based calculations of quasiparticle properties for finite systems is presented, in which the screened interaction is obtained directly from a linear response calculation of the density-density correlation function. The conserving nature of our results is shown by explicit evaluation of the $f$-sum rule. As an application, energy renormalizations and level broadenings are calculated for the closed-shell Na$_9^+$ and Na$_{21}^+$ clusters, as well as for Na$_4$. Pronounced improvements of conserving approximations to RPA-level results are obtained.