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- Title
Dipolar spin-waves and tunable band gap at the Dirac points in the 2D magnet ErBr<sub>3</sub>.
- Authors
Wessler, Christian; Roessli, Bertrand; Krämer, Karl W.; Stuhr, Uwe; Wildes, Andrew; Braun, Hans B.; Kenzelmann, Michel
- Abstract
Topological magnon insulators constitute a growing field of research for their potential use as information carriers without heat dissipation. We report an experimental and theoretical study of the magnetic ground-state and excitations in the van der Waals two-dimensional honeycomb magnet ErBr3. We show that the magnetic properties of this compound are entirely governed by the dipolar interactions which generate a continuously degenerate non-collinear ground-state on the honeycomb lattice with spins confined in the plane. We find that the magnon dispersion exhibits Dirac-like cones when the magnetic moments in the ground-state are related by time-reversal and inversion symmetries associated with a Berry phase π as in single-layer graphene. A magnon band gap opens when the dipoles are rotated away from this state, entailing a finite Berry curvature in the vicinity of the K and K' Dirac points. Our results illustrate that the spin-wave dispersion of dipoles on the honeycomb lattice can be reversibly controlled from a magnetic phase with Dirac cones to a topological antiferromagnetic insulator with non-trivial valley Chern number. Magnonic devices, based on the physics of spin-waves, are a potential alternative to process and store information that consume less energy and van der Waals crystals are candidate materials for such applications. Here, the authors investigate the magnetic ground state and spin-wave spectrum of ErBr3 finding that the dipolar interactions play a dominant role and allow for continuous control of topological excitations.
- Subjects
BAND gaps; SPIN waves; GEOMETRIC quantum phases; TOPOLOGICAL insulators; MAGNETS; MAGNETIC moments
- Publication
Communications Physics, 2022, Vol 5, Issue 1, p1
- ISSN
2399-3650
- Publication type
Article
- DOI
10.1038/s42005-022-00965-5