Abstract
In two-dimensional honeycomb ferromagnets, bosonic magnon quasiparticles (spin waves) may either behave as massless Dirac fermions or form topologically protected edge states. The key ingredient defining their nature is the next-nearest-neighbor Dzyaloshinskii-Moriya interaction that breaks the inversion symmetry of the lattice and discriminates chirality of the associated spin-wave excitations. Using inelastic neutron scattering, we find that spin waves of the insulating honeycomb ferromagnet CrI3 (TC=61 K) have two distinctive bands of ferromagnetic excitations separated by a ∼4 meV gap at the Dirac points. These results can only be understood by considering a Heisenberg Hamiltonian with Dzyaloshinskii-Moriya interaction, thus providing experimental evidence that spin waves in CrI3 can have robust topological properties potentially useful for dissipationless spintronic applications.
| Original language | English |
|---|---|
| Article number | 041028 |
| Journal | Physical Review X |
| Volume | 8 |
| Issue number | 4 |
| DOIs | |
| State | Published - Nov 14 2018 |
Funding
The neutron scattering work at Rice is supported by the U.S. NSF Grant No. DMR-1700081 (P. D.). The single-crystal synthesis work was supported by the Robert A. Welch Foundation Grant No. C-1839 (P. D.). The work of J. H. C. was supported by the National Research Foundation of Korea (No. NRF-2016R1D1A1B03934157; No. NRF-2017K1A3A7A09016303). Research at Oak Ridge National Laboratory’s Spallation Neutron Source was supported by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for U.S. DOE under Contract No. DE-AC05-00OR22725.