Anti-symmetric Compton scattering in LiNiPO$_4$: Towards a direct probe of the magneto-electric multipole moment

TL;DR

This study combines theory and experiment to explore anti-symmetric Compton scattering in LiNiPO$_4$ as a potential method to detect magneto-electric multipoles, revealing small but measurable effects that encourage further research.

Contribution

It provides the first combined theoretical and experimental analysis of anti-symmetric Compton profiles related to magneto-electric multipoles in LiNiPO$_4$, highlighting the small magnitude of the effect.

Findings

Computed anti-symmetric profile is about four orders of magnitude smaller than the total profile.

Experimental measurements are consistent with theoretical predictions within error margins.

Results motivate searching for materials with larger anti-symmetric Compton effects.

Abstract

We present a combined theoretical and experimental investigation of the anti-symmetric Compton profile in LiNiPO$_4$ as a possible probe for magneto-electric toroidal moments. Understanding as well as detecting such magneto-electric multipoles is an active area of research in condensed matter physics. Our calculations, based on density functional theory, indicate an anti-symmetric Compton profile in the direction of the $t_y$ toroidal moment in momentum space, with the computed anti-symmetric profile around four orders of magnitude smaller than the total profile. The difference signal that we measure is consistent with the computed profile, but of the same order of magnitude as the statistical errors and systematic uncertainties of the experiment. Our results motivate further theoretical work to understand the factors that influence the size of the anti-symmetric Compton profile, and to identify materials exhibiting larger effects.