EMS Measurement of the Valence Spectral Function of Silicon - a test of Many-body Theory

TL;DR

This study measures silicon's spectral function using electron momentum spectroscopy and compares it with advanced theoretical calculations, finding the cumulant expansion better describes satellite features than GW.

Contribution

It provides high-resolution experimental data on silicon's spectral function and evaluates the accuracy of GW and cumulant expansion theories in predicting satellite structures.

Findings

Band dispersions match both theories

GW predicts a satellite not observed experimentally

Cumulant expansion better describes satellite shape and momentum dependence

Abstract

The spectral function A(q,omega) of silicon has been measured along a number of symmetry directions using high-energy high-resolution electron momentum spectroscopy. It is compared with first-principles calculations based on the interacting one-electron Green's function which is evaluated in the GW and the cumulant expansion approximations. Positions of the quasiparticle peaks (dispersion), their widths (lifetimes), and the extensive satellite structures are measured over a broad range of energies and momenta. The band dispersions are well described by both calculations, but the satellite predicted by the GW calculation is not observed. Unlike the GW calculation, the cumulant expansion calculation gives a significantly better description of the shape and momentum dependence of the satellite structure, presenting a promising approach for studying high-energy excitations.The spectral function A(q,omega) of silicon has been measured along a number of symmetry directions using high-energy high-resolution electron momentum spectroscopy. It is compared with first-principles calculations based on the interacting one-electron Green's function which is evaluated in the GW and the cumulant expansion approximations. Positions of the quasiparticle peaks (dispersion), their widths (lifetimes), and the extensive satellite structures are measured over a broad range of energies and momentum dependence of the satellite structure, presenting a promising approach for studying high-energy excitations.