Twisted magnon frequency combs in ferromagnetic nanorings

Abstract

We report the emergence of twisted magnon frequency combs (tMFCs) and their higher-order modes in ferromagnetic nanorings, arising from strong nonlinear coupling between vortex-core gyration and azimuthal spin-wave modes. The comb lines carry distinct orbital angular momentum with quantum numbers spaced by unity, and their formation obeys selection rules governed by simultaneous conservation of energy and angular momentum. We demonstrate that the hole diameter serves as a powerful tuning parameter: reducing the hole size preserves the conventional tMFC, whereas increasing it introduces an additional magnon mode that dramat?ically densifies the comb via four-wave mixing, boosting the sideband multiplicity by an order of magnitude. Moreover, an external in-plane magnetic field enables continuous, reversible tuning of the comb spacing by dis?placing the vortex core and modifying its confinement potential, with the hole-induced geometric pinning giving rise to asymmetric switching and hysteresis under opposite field polarities. Our results establish the tMFC as a versatile platform for nonlinear magnonics, with potential applications in tunable frequency comb generation and precision metrology.