Chiral and flat-band magnetic quasiparticles in ferromagnetic and metallic kagome layers

Abstract

Magnetic kagome metals are a promising platform to develop unique quantum transport and optical phenomena caused by the interplay between topological electronic bands, strong correlations, and magnetic order. This interplay may result in exotic quasiparticles that describe the coupled electronic and spin excitations on the frustrated kagome lattice. Here, we observe novel elementary magnetic excitations within the ferromagnetic Mn kagome layers in TbMn₆Sn₆ using inelastic neutron scattering. We observe sharp, collective acoustic magnons and identify flat-band magnons that are localized to a hexagonal plaquette due to the special geometry of the kagome layer. Surprisingly, we observe another type of elementary magnetic excitation; a chiral magnetic quasiparticle that is also localized on a hexagonal plaquette. The short lifetime of localized flat-band and chiral quasiparticles suggest that they are hybrid excitations that decay into electronic states.

S. X. M. Riberolles et al. study the kagome Chern insulator TbMn₆Sn₆ via inelastic neutron scattering. They observe signatures of chiral and flat-band magnons, which are highly localized in real space and strongly damped in the time domain.