# Regensburg 2019 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 4: Topological insulators and spin-dependent transport phenomena

### MA 4.8: Vortrag

### Montag, 1. April 2019, 11:30–11:45, H52

**Magnonic Weyl states in Cu**_{2}**OSeO**_{3} — •L. Zhang^{1}, Y. A Onykiienko^{2}, P.M. Buhl^{1}, Y. V Tymoshenko^{2}, P. Čermák^{3,4}, A. Schneidewind^{3}, S. Blügel^{1}, D.S. Inosov^{2}, and Y. Mokrousov^{1,5} — ^{1}PGI and IAS, FZ Jülich and JARA, 52425 Jülich, Germany — ^{2}IFMP, TU Dresden, D-01069 Dresden, Germany — ^{3}JCNS, FZ Jülich GmbH, Outstation at Heinz MLZ, Lichtenbergstraße 1, D-85747 Garching, Germany — ^{4}Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, 121 16, Praha, Czech Republic — ^{5}Institute of Physics, JGU Mainz, 55099 Mainz, Germany

The multiferroic ferrimagnet Cu_{2}OSeO_{3} with a chiral crystal structure has recently attracted significant attention due to the emergence of a skyrmion order in this material [1]. Here the topological properties of its magnon excitations were investigated by linear spin-wave theory and inelastic neutron scattering. Considering only the Heisenberg exchange interactions, two Weyl points are observed at high symmetry points with topological charges ± 2. Each Weyl point splits into two as the symmetry of the system is further reduced, if in addition the nearest neighbor Dzyaloshinsky-Moriya interaction is taken into consideration, which is decisive for obtaining an accurate fit to the experiment results. The predicted topological properties are verified by surface state and Chern number analysis. In addition, we predict that a sizeable thermal Hall conductivity can be associated with the emergence of the Weyl points, the position of which can be tuned by changing the crystal symmetry of the material.
[1] Portnichenko, P. Y. et al., Nat. Commun. 7, 10725 (2016)