Many-body and QED effects in electron-atom inelastic scattering in EELS

TL;DR

This paper develops a quantum electrodynamics framework to accurately calculate inelastic electron scattering in EELS, accounting for many-body effects and atomic relaxation, leading to improved spectral predictions.

Contribution

It introduces a QED-based perturbative approach for inelastic scattering, incorporating atomic relaxation and many-body correlations, enhancing the understanding of EELS spectra.

Findings

Good agreement between calculated and experimental spectra for DyScO3.

Correlation effects significantly influence the differential cross section near ionization threshold.

The method improves spectral interpretation by including atomic and many-body effects.

Abstract

The elemental composition and electronic structure of materials analyzed by electron energy loss spectroscopy (EELS) are probed by the inner-shell ionization of atoms. This is a localized process that can be approximated by the scattering of an electron beam from a free atom. We calculate the inelastic differential cross section perturbatively within the framework of quantum electrodynamics (QED). The interaction between the incoming electron and the atom factorizes into a high-energy electron term and the atomic transition current. The matrix elements of the transition current are computed within the relaxed Dirac Hartree Fock method. We analyze the correlation effects arising from the relaxation of the atomic orbitals induced by the creation of a core hole. These effects are particularly relevant in quantum many-body systems and have a significant impact on the shape of the differential cross section near the ionization threshold in EELS spectra. In addition to the continuum, we calculate the discrete excitation spectrum of $\mathrm{DyScO_3}$ using crystal-field multiplet theory. The calculated spectrum shows very good agreement with experimental EELS data.