  An explicit realistic model featuring a supercooled phase transition, which
allows us to explain the background of gravitational waves recently detected by
pulsar timing arrays, is constructed. In this model the phase transition
corresponds to radiative symmetry breaking (and mass generation) in a dark
sector featuring a dark photon associated with the broken symmetry. The
completion of the transition is ensured by a non-minimal coupling between
gravity and the order parameter and fast reheating occurs thanks to a
preheating phase. Finally, it is also shown that the model leads to primordial
black hole production.
