Damped Topological Magnons in the Kagom\'{e}-Lattice Ferromagnets

TL;DR

This paper shows how interactions, especially Dzyaloshinskii-Moriya coupling, cause significant damping of high-energy magnons in kagome lattice ferromagnets, challenging the free-particle magnon picture.

Contribution

It reveals the non-perturbative damping effects of interactions on magnons in frustrated kagome ferromagnets, highlighting the role of anharmonic coupling and degeneracy.

Findings

Strong magnon damping due to anharmonic interactions

Dzyaloshinskii-Moriya interaction facilitates damping

High-energy magnon modes are significantly affected

Abstract

We demonstrate that interactions can substantially undermine the free-particle description of magnons in ferromagnets on geometrically frustrated lattices. The anharmonic coupling, facilitated by the Dzyaloshinskii-Moriya interaction, and a highly-degenerate two-magnon continuum yield a strong, non-perturbative damping of the high-energy magnon modes. We provide a detailed account of the effect for the $S=1/2$ ferromagnet on the kagom\'e lattice and propose further experiments.