Why is the bandwidth of sodium observed to be narrower in photoemission experiments?

TL;DR

This paper explains the observed narrowing of sodium's bandwidth in photoemission experiments by analyzing the non-local self-energy effects on quasi-particle energies, revealing a misinterpretation in previous analyses.

Contribution

It clarifies the role of non-local self-energy corrections in photoemission data, challenging the traditional nearly-free-electron model assumptions.

Findings

Self-energy correction increases monotonically with wavenumber

Incorrect attribution of self-energy effects leads to perceived bandwidth narrowing

Revised interpretation aligns experimental observations with theoretical predictions

Abstract

The experimentally predicted narrowing in the bandwidth of sodium is interpreted in terms of the non-local self-energy effect on quasi-particle energies of the electron liquid. The calculated self-energy correction is a monotonically increasing function of the wavenumber variable. The usual analysis of photo-emission experiments assumes the final state energies on the nearly-free-electron-like model and hence it incorrectly ascribes the non-local self-energy correction to the final state energies to the occupied state energies, thus leading to a seeming narrowing in the bandwidth.