Many-body effects on the electron-positron momentum density in simple and transition metals: Comparison with positron annihilation spectroscopy data

Abstract

This paper deals with the influence of many-body effects on the electron-positron ($e$-$p$) momentum density in simple and transition metals. Five theoretical approaches to calculating $e$-$p$ momentum densities are confronted with three-dimensional densities, reconstructed from two-dimensional angular correlation of annihilation radiation experimental spectra in Mg, Cd, Cu, and Y. It is shown that a proper description of $e$-$p$ correlations has to include the lattice-periodical crystal potential as is done, e.g., in the Bloch-modified ladder theory. Moreover, it is demonstrated that electron-electron correlations are visible not only in Compton scattering but also in positron annihilation experiments.