Exact solutions to nonlinear symmetron theory: One- and two-mirror systems. II.

We derive the exact analytical solutions to the symmetron field theory equations in the presence of a one- or two-mirror system in the case of a spontaneously broken phase in vacuum as well as in matter. This complements a similar analysis performed in a previous article, in which the symmetron is in the spontaneously broken phase in vacuum but in the symmetric phase in matter. Here again, the one-dimensional equations of motion are integrated exactly for both systems, and their solutions are expressed in terms of Jacobi elliptic functions. In the case of two parallel mirrors, the equations of motion provide also in this case a discrete set of solutions with an increasing number of nodes and energies. The solutions obtained herein can be applied to qBOUNCE experiments, to neutron interferometry, and to the calculation of the symmetron-field-induced "Casimir force" in the CANNEX experiment and allow us to extend the investigation to hitherto unavailable regions in symmetron parameter space.