Bistability in dissipatively coupled cavity magnonics*

Dissipative coupling is characterized by the cooperation of external dampings to a common reservoir and shows energy level attraction in the dispersion. In this study, a magnetic material (yttrium iron garnet) is placed at the node of rf magnetic field in a Fabry-Perot-like microwave cavity such that the magnons and cavity photons are dissipatively coupled, and nonlinear effect is directly observed by driving the cavity with high power and measuring through its transmission. Such a dissipatively coupled hybridized system results in bistable behaviors, manifesting themselves as clockwise, counterclockwise, and butterflylike hysteresis loops by modulating the frequency detuning with respect to the coupling strength. The experimental results are well fitted and explained as a nonlinear Duffing oscillator dissipatively coupled with a harmonic oscillator. In addition, the coupled oscillators model could determine the critical condition required to produce bistability effects in a dissipatively coupled system. The model describing the coupling between magnon and cavity subsystems is generic and can be widely used in dissipatively coupled nonlinear systems involving Duffing oscillator and harmonic oscillator. This research sheds light upon potential applications of dissipatively coupled system such as creating a lower power threshold for nonlinearity and making enhanced anharmonicity sensors.