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 ℓ. 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 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.
| Original language | English |
|---|---|
| Article number | 097201 |
| Journal | Physical Review Letters |
| Volume | 128 |
| Issue number | 9 |
| DOIs | |
| State | Published - Mar 4 2022 |
Bibliographical note
Publisher Copyright:© 2022 American Physical Society.
Funding
We acknowledge helpful discussions with Satoshi Okamoto. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The research by P. L. was supported by the Scientific Discovery through Advanced Computing (SciDAC) program funded by the U.S. Department of Energy, Office of Science, Advanced Scientific Computing Research and Basic Energy Sciences, Division of Materials Sciences and Engineering. The work by S. E. N. is supported by the Quantum Science Center (QSC), a National Quantum Information Science Research Center of the U.S. Department of Energy (DOE). This work has been partially supported by U.S. DOE Grant No. DE-FG02-13ER41967. ORNL is managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy. The U.S. Government retains, and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so for U.S. Government purposes.
| Funders | Funder number |
|---|---|
| National Quantum Information Science Research Center | |
| Quantum Science Center | |
| U.S. Department of Energy | DE-FG02-13ER41967 |
| Office of Science | |
| Advanced Scientific Computing Research | |
| Oak Ridge National Laboratory | DE-AC05-00OR22725 |
| Division of Materials Sciences and Engineering |