Scientific Achievement
Chiral excitations in the kagome layers of TbMn6Sn6, observed with inelastic neutron scattering (INS), behave like
localized magnetic quasiparticles.
Significance and Impact
Kagome metals are platforms for a variety of charge and magnetic instabilities. In TbMn6Sn6, strong ferromagnetism exists in the Mn kagome layers, yet we find vortex-like chiral magnetic excitations can emerge. These chiral ”particles” are not predicted from magnetic modeling, signaling new physics.
Research Details
- INS measurements were performed at the ARCS spectrometer at the SNS.
- High energy magnetic excitations are very broad in energy and momentum.
- Analysis of their momentum dependence reveals two localized excitations: a “flat-band” magnon and a novel chiral excitation.
- Localized flat-band modes are expected from modeling, whereas the chiral modes are unexpected and truly anomalous. Both modes have a metallic-like character due to hybridization with conduction electrons.
- Chiral modes can be observed from 180 meV down to 30 meV or lower, suggesting that the FM kagome layer is close to a chiral instability.
S. X. M. Riberolles, et al., Chiral and flat-band magnetic quasiparticles in ferromagnetic and metallic kagome layers. Nat. Comm. 15, 1592 (2024). https://doi.org/10.1038/s41467-024-45841-8.