Pump-induced magnon anticrossing due to three-magnon splitting and confluence

TL;DR

This paper proposes a mechanism for magnon-magnon level repulsion caused by three-magnon scattering, where nonlinear interactions induce an anticrossing effect similar to strong magnon-photon coupling.

Contribution

It introduces a novel explanation for magnon anticrossing via three-magnon splitting and confluence, highlighting a nonlinear back-action effect in a pumped YIG sphere.

Findings

Observation of magnon spectrum bending effect

Identification of three-magnon scattering as the cause

Analogy to magnon-photon strong coupling

Abstract

We present a plausible mechanism for achieving magnon-magnon level repulsion spectrum originating from the oscillation between the splitting and confluence in a three-magnon scattering process. When a magnetostatic mode on a YIG sphere is pumped by a microwave signal near the magnon resonance frequency with an increasing amplitude, the generated magnon condensate at half of the pumping frequency exerts a back-action to the original magnon mode. Such a strong nonlinear coupling manifests a striking feature of a 'bending effect' of the magnetostatic mode spectra, akin to the anti-crossing observed in a strongly coupled magnon-photon system.