Abstract
Dirac matters provide a platform for exploring the interplay of their carriers with other quantum phenomena. has been proposed to be a magnetic Weyl semimetal and provides an excellent platform to study the coupling between Weyl fermions and magnons. Here, we report comprehensive inelastic neutron scattering (INS) measurements on single crystals of , which have been well characterized by magnetization and magnetotransport measurements, both of which demonstrate that the material is a topologically nontrivial semimetal. The INS spectra clearly show a spin gap of meV. The dispersion in the magnetic Mn layer extends up to about 76 meV, while that between the layers has a narrow band width of 6 meV. We find that the linear spin-wave theory using a Heisenberg spin Hamiltonian can reproduce the experimental spectra with the following parameters: a nearest-neighbor ( meV) and next-nearest-neighbor in-plane exchange interaction ( meV), interlayer exchange coupling ( meV), and spin anisotropy constant ( meV). Despite the coexistence of Weyl fermions and magnons, we find no clear evidence that the magnetic dynamics are influenced by the Weyl fermions in , possibly because that the Weyl fermions and magnons reside in the Sb and Mn layers separately, and the interlayer coupling is weak due to the quasi-two-dimensional nature of the material, as also evident from the small of meV.
- Received 2 December 2019
- Revised 13 February 2020
- Accepted 17 March 2020
DOI:https://doi.org/10.1103/PhysRevB.101.134408
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