Highly Dispersive Scattering From Defects In Non-Collinear Magnets

TL;DR

This paper reveals that point-like defects in non-collinear magnets cause a highly dispersive magnon scattering structure, driven by umklapp processes from impurity-induced spin textures, challenging the conventional view of momentum-independent scattering.

Contribution

It demonstrates the dispersive nature of magnon scattering from defects in non-collinear magnets and links it to impurity-induced spin textures and umklapp scattering.

Findings

Dispersive magnon scattering structure observed

Scattering momentum dependence set by magnon dispersion

Impurity-induced spin textures cause umklapp scattering

Abstract

We demonstrate that point-like defects in non-collinear magnets give rise to a highly dispersive structure in the magnon scattering, violating a standard paradigm of its momentum independence. For a single impurity spin coupled to a prototypical non-collinear antiferromagnet we find that the resolvent is dominated by a distinct dispersive structure with its momentum-dependence set by the magnon dispersion and shifted by the ordering vector. This feature is a consequence of umklapp scattering off the impurity-induced spin texture, which arises due to the non-collinear ground state of the host system. Detailed results for the staggered and uniform magnetization of this texture as well as the T-matrix from numerical linear spin-wave theory are presented.