Discovery of terahertz-frequency orbitally-coupled magnons in a kagome ferromagnet

TL;DR

This paper reports the discovery of high-frequency terahertz orbitally-coupled magnons in a kagome ferromagnet, revealing a new class of magnons linked to orbital magnetic moments with potential for spintronic applications.

Contribution

It provides the first experimental observation of terahertz orbitally-coupled magnons in a topological kagome ferromagnet, expanding understanding of magnon spectra beyond conventional spin waves.

Findings

Detected magnon resonances at 0.61 and 0.49 THz in Co3Sn2S2

Magnons originate from strong coupling of spin and orbital moments

Resonances surpass previous magnon frequencies in ferromagnets

Abstract

In ferromagnetic materials, magnons - quanta of spin waves - typically resonate in the gigahertz range. Beyond conventional magnons, while theoretical studies have predicted magnons associated with orbital magnetic moments, their direct observation has remained challenging. Here, we present the discovery of two distinct terahertz orbitally-coupled magnon resonances in the topological kagome ferromagnet Co3Sn2S2. Using time-resolved Kerr rotation spectroscopy, we pinpoint two magnon resonances at 0.61 and 0.49 THz at 6 K, surpassing all previously reported magnon resonances in ferromagnets due to strong magnetocrystalline anisotropy. These dual modes originate from the strong coupling of localized spin and orbital magnetic moments. These findings unveil a novel category of magnons stemming from orbital magnetic moments, and position Co3Sn2S2 as a promising candidate for high-speed terahertz spintronic applications