Controllable quantum phase transition in a double-cavity magnonic system

We propose a theoretical model to study the quantum phase transition in a double-cavity magnonic system. We find that the system exhibits a second-order phase transition from a parity-symmetric phase to a parity-symmetry-broken phase or a first-order phase transition from a parity-symmetric phase to a bistable phase when the driving strength of one cavity is above a critical value. We obtain the phase diagram, the critical point, and the corresponding critical exponent to characterize the phase transition. We can identify different phase transitions by the different behaviors of the mean magnon number and correlation fluctuation in the vicinity of the critical point. In particular, we show that the phase transition in one cavity can be precisely and efficiently controlled by adjusting the parameters of the other cavity, which suggests that we can easily observe the phase transition at low driving strength in experiment. The effects of additional microwave pulses on the dynamical behavior of the phase-transition observable and the experimental feasibility of our theoretical scheme are discussed as well.