  We investigate the universally non-equilibrium dynamics of superradiant phase
transition in the anisotropic quantum Rabi model. By introducing position and
momentum operators, we obtain the ground states and their excitation gaps for
both normal and superradiant phases via perturbation theory. We analytically
extract the critical exponents from the excitation gap and the diverging length
scale near the critical point, and find that the critical exponents are
independent upon the anisotropy ratio. Moreover, by simulating the real-time
dynamics across the critical point, we numerically extract the critical
exponents from the phase transition delay and the diverging length scale, which
are well consistent with the analytical ones. Our study provides a dynamic way
to explore universal critical behaviors in the quantum Rabi model.
