Abstract
Topological magnons are emergent quantum spin excitations featured by magnon bands crossing linearly at the points dubbed nodes, analogous to fermions in topological electronic systems. Experimental realisation of topological magnons in three dimensions has not been reported so far. Here, by measuring spin excitations (magnons) of a three-dimensional antiferromagnet Cu3TeO6 with inelastic neutron scattering, we provide direct spectroscopic evidence for the coexistence of symmetry-protected Dirac and triply degenerate nodes, the latter involving three-component magnons beyond the Dirac-Weyl framework. Our theoretical calculations show that the observed topological magnon band structure can be well described by the linear-spin-wave theory based on a Hamiltonian dominated by the nearest-neighbour exchange interaction J 1. As such, we showcase Cu3TeO6 as an example system where Dirac and triply degenerate magnonic nodal excitations coexist, demonstrate an exotic topological state of matter, and provide a fresh ground to explore the topological properties in quantum materials.
Original language | English |
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Article number | 2591 |
Journal | Nature Communications |
Volume | 9 |
Issue number | 1 |
DOIs | |
State | Published - Dec 1 2018 |
Funding
Work at Nanjing University was supported by National Natural Science Foundation of China with Grant Nos. 11674157, 11774152, 11374138, 11674158 and 11525417, National Key Projects for Research & Development of the Ministry of Science and Technology of China with Grant No. 2016YFA0300401, and Fundamental Research Funds for the Central Universities with Grant No. 020414380105. The research at Oak Ridge National Laboratory’s Spallation Neutron Source was sponsored by the US Department of Energy, office of Basic Energy Sciences, Scientific User Facilities Division. We thank Jian Sun, S. A. Owerre, Yuan Li, and Ka Shen for stimulating discussions.