Non-Reciprocal Zone Boundary Magnon Propagation in Cu$_2$OSeO$_3$

TL;DR

This study demonstrates strong non-reciprocal magnon propagation at the zone boundary in the chiral magnet Cu$_2$OSeO$_3$, revealing persistent directional effects at high momenta with minimal damping, relevant for magnonic technologies.

Contribution

It provides the first observation of non-reciprocal magnon propagation at the Brillouin zone boundary in a chiral magnet using inelastic neutron scattering.

Findings

Non-reciprocal effects are strongest between zone corner and edge mid-point.

Magnons exhibit very little damping, suitable for high-frequency applications.

Non-reciprocity persists at high momenta, beyond low-momentum regimes.

Abstract

Inelastic neutron scattering in the chiral magnet Cu$_2$OSeO$_3$ reveals strong non-reciprocal effects on magnon propagation at the boundary of the nuclear Brillouin zone. The non-reciprocal response is strongest at a central position between the zone corner and edge mid-point. We explain these results using an effective linear spin-wave model. While directional effects in chiral magnets have so far only been known to exist at low momenta close to the center of the Brillouin zone, the present study shows that non-reciprocity persists at the highest possible reduced momenta. The observed magnons show very little damping within the limits of our experimental resolution, making them of great interest for the fundamental research on compact, high-frequency magnonic applications.