Out-of-time-order correlator in the quantum Rabi model

We investigate signatures of chaos and equilibration in the quantum Rabi model, which exhibits a phase transition when ratio atomic level-splitting to bosonic frequency grows infinity. show that out-of-time-order correlator derived from Loschmidt echo signal quickly saturates normal reveals exponential growth superradiant is associated with onset chaos. Furthermore, we effective time-averaged dimension system can be large compared spin size leads suppression temporal fluctuations system.