Bistability of Cavity Magnon Polaritons

TL;DR

This paper reports the first observation of magnon-polariton bistability in a cavity magnonics system, revealing sharp frequency switchings and hysteresis behaviors linked to Kerr nonlinearity and magnetic field tuning.

Contribution

It demonstrates the experimental realization of magnon-polariton bistability and explains it through Kerr nonlinearity, with observations of different hysteresis behaviors based on crystallographic orientation.

Findings

Observation of sharp frequency switchings in CMPs

Different hysteresis loops depending on YIG sphere orientation

Bistability of magnons and cavity photons when tuning magnetic field

Abstract

We report the first observation of the magnon-polariton bistability in a cavity magnonics system consisting of cavity photons strongly interacting with the magnons in a small yttrium iron garnet (YIG) sphere. The bistable behaviors are emerged as sharp frequency switchings of the cavity magnon-polaritons (CMPs) and related to the transition between states with large and small number of polaritons. In our experiment, we align, respectively, the [100] and [110] crystallographic axes of the YIG sphere parallel to the static magnetic field and find very different bistable behaviors (e.g., clockwise and counter-clockwise hysteresis loops) in these two cases. The experimental results are well fitted and explained as being due to the Kerr nonlinearity with either positive or negative coefficient. Moreover, when the magnetic field is tuned away from the anticrossing point of CMPs, we observe simultaneous bistability of both magnons and cavity photons by applying a drive field on the lower branch.