1. Dirac magnons, nodal lines, and nodal plane in elemental gadolinium
- Author
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Scheie, Allen, Laurell, Pontus, McClarty, Paul A., Granroth, Garrett E., Stone, Matt B., Moessner, Roderich, and Nagler, Stephen E.
- Subjects
Condensed Matter - Strongly Correlated Electrons - 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 $K$ and nodal planes at half integer $\ell$. We find an anisotropic intensity winding around the $K$-point Dirac magnon cone, which is interpreted to indicate Berry phase physics. Using linear spin wave theory calculations, we show the nodal lines have non-trivial 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., Comment: 4 pages, 4 figures, plus four pages supplemental information. Accompanying paper to arXiv:2107.11370
- Published
- 2021
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