Experimental determination of the state-dependent enhancement of the electron-positron momentum density in solids

TL;DR

This study investigates how the enhancement of electron-positron momentum density varies with electronic state in metals, providing a quantitative, parameter-free measurement and a predictive correction model for positron annihilation experiments.

Contribution

It offers the first quantitative, state-dependent measurement of electron-positron momentum density enhancement in metals, independent of local electron density parameterizations.

Findings

Measured state-dependent enhancement factors for s, p, d states in metals.

Proposed an empirical correction model that accurately reproduces observed enhancements.

Developed a predictive model applicable to various positron annihilation techniques.

Abstract

The state-dependence of the enhancement of the electron-positron momentum density is investigated for some transition and simple metals (Cr, V, Ag and Al). Quantitative comparison with linearized muffin-tin orbital calculations of the corresponding quantity in the first Brillouin zone is shown to yield a measurement of the enhancement of the s, p and d states, independent of any parameterizations in terms of the electron density local to the positron. An empirical correction that can be applied to a first-principles state-dependent model is proposed that reproduces the measured state-dependence very well, yielding a general, predictive model for the enhancement of the momentum distribution of positron annihilation measurements, including those of angular correlation and coincidence Doppler broadening techniques.