Abstract
We investigate the magnetic excitations of elemental gadolinium (Gd) using inelastic neutron scattering, showing that Gd is a Dirac magnon material with nodal lines at and nodal planes at half integer . We find an anisotropic intensity winding around the -point Dirac magnon cone, which is interpreted to indicate Berry phase physics. Using linear spin wave theory calculations, we show the nodal lines have nontrivial Berry phases, and topological surface modes. We also discuss the origin of the nodal plane in terms of a screw-axis symmetry, and introduce a topological invariant characterizing its presence and effect on the scattering intensity. Together, these results indicate a highly nontrivial topology, which is generic to hexagonal close packed ferromagnets. We discuss potential implications for other such systems.
- Received 23 July 2021
- Accepted 12 January 2022
DOI:https://doi.org/10.1103/PhysRevLett.128.097201
© 2022 American Physical Society
Physics Subject Headings (PhySH)
Viewpoint
Topological Magnetism Turns Elementary
Published 2 March 2022
Neutron scattering experiments provide the evidence of massless spin waves called Dirac magnons in a single-element magnetic crystal, offering a new window into topological magnetism.
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