Many-body effects observed in the positron annihilation experiment

TL;DR

This study investigates many-body electron-positron and electron-electron interactions in solids, demonstrating the importance of lattice potential and showing that e-e correlations influence positron annihilation measurements.

Contribution

It highlights the significance of lattice potential in modeling e-p correlations and clarifies that e-e correlations do not cancel out in positron annihilation experiments.

Findings

Lattice potential significantly affects e-p correlation effects.

e-e correlations are observable in positron annihilation, not just in scattering.

Proper theoretical description requires periodic lattice potential, e.g., BML theory.

Abstract

This paper is devoted to study many-body effects in the positron annihilation experiment, both electron-positron (e-p) and electron-electron (e-e) correlations. Various theories of the e-p interaction in real solids were used to verify them by comparing theoretical and experimental e-p momentum densities in Cu and Y. We show that the lattice potential has an essential influence on the e-p correlation effects, i.e. their proper description must be done via periodic lattice potential as e.g. in the Bloch Modified Ladder (BML) theory. Moreover, it is not true that that the dynamic parts of the direct e-p and e-e interactions cancel each other because e-e correlations are observed not only in the Compton scattering but also in the positron annihilation experiments. Keywords: positron annihilation, Compton scattering, momentum densities, many-body effects