Topological magnon bands in a room-temperature kagome magnet
Heda Zhang, Xiaozhou Feng, Thomas Heitmann, А. И. Колесников, M. B. Stone, Yuan-Ming Lu, Xianglin Ke
Abstract
Topological magnon is a vibrant research field gaining more and more attention in the past few years. Among many theoretical proposals and limited experimental studies, ferromagnetic kagome lattice emerges as one of the most elucidating systems. Here we report neutron scattering studies of ${\mathrm{YMn}}_{6}{\mathrm{Sn}}_{6}$, a metallic system consisting of ferromagnetic kagome planes. This system undergoes a commensurate-to-incommensurate antiferromagnetic phase transition upon cooling with the incommensurability along the out-of-plane direction. We observe magnon band gap opening at the symmetry-protected $K$ points and ascribe this feature to the antisymmetric Dzyaloshinskii-Moriya (DM) interactions. Our observation supports the existence of topological Dirac magnons in both the commensurate collinear and incommensurate coplanar magnetic orders, which is further corroborated by symmetry analysis. This finding places ${\mathrm{YMn}}_{6}{\mathrm{Sn}}_{6}$ as a promising candidate for room-temperature magnon spintronics applications.