Why paramagnetic chiral correlations in the long wavelength limit do not contribute to muon-spin relaxation

TL;DR

This paper demonstrates that muon-spin relaxation techniques do not detect paramagnetic chiral correlations in the long wavelength limit, indicating they only probe non-chiral magnetic correlations.

Contribution

It provides a theoretical analysis showing that muon-spin relaxation is insensitive to paramagnetic chiral correlations at long wavelengths, clarifying the technique's limitations.

Findings

Muon-spin relaxation does not detect paramagnetic chiral correlations.

The relaxation rate probes only non-chiral magnetic correlations.

Chiral correlations are invisible to muon-spin relaxation in the long wavelength limit.

Abstract

A crystal structure that cannot be superposed on its mirror image by any combination of rotations and translations is classified as chiral. Such crystal structures have gained importance in recent years since they are prone to host unconventional magnetic orders and to exhibit topological magnetic textures. These properties result from the Dzyaloshinskii-Moriya antisymmetric exchange interaction which is authorized when space inversion is broken. While recent reports have shown the muon spin rotation and relaxation technique to provide unique information about structural and dynamical properties which are specific to chiral magnets in their ordered phase, the question here is whether this technique is sensitive to paramagnetic chiral correlations that are observed in neutron scattering experiments above the critical temperature. In the relevant long wavelength limit, it is shown that they do not contribute to the relaxation rate, which in turn only probes non-chiral correlations.