Spin-wave emission in skyrmion-antiskyrmion bilayers*

The use of spin waves (SWs) as data carriers in spintronic and magnonic logic devices offers operation at low power consumption, free of Joule heating. Nevertheless, the controlled emission and propagation of SWs in magnetic materials remains a significant challenge. Here, we propose that skyrmion-antiskyrmion bilayers form topological charge dipoles and act as efficient sub-100 nm SW emitters when excited by in-plane ac magnetic fields [1]. The propagating SWs have a preferred radiation direction, with clear dipole signatures in their radiation pattern, suggesting that the bilayer forms a SW antenna. The characteristics of the emitted SWs are linked to the topology of the source, allowing for full control of the SW features, including their amplitude, preferred direction of propagation, and wavelength. I will also discuss the response of skyrmions under an oscillating magnetic field gradient. In a recent work, we treated the unavoidable impact of the driving field on the magnon bath and demonstrated that, new time-dependent dissipation terms arise for the skyrmion, which result in a new type of unidirectional propagation [2]. This work opens up new possibilities to control skyrmion dissipation under certain non-equilibrium protocols.

[1] Spin Wave Radiation by a Topological Charge Dipole, S. A. Diaz, T. Hirosawa, D. Loss, and C. Psaroudaki, Nano Lett. 20, 9, 6556 (2020).
[2] Skyrmions Driven by Intrinsic Magnons, C. Psaroudaki and D. Loss, Phys. Rev. Lett. 120, 237203 (2018).