A model is developed for a superconductor under an external dynamic pair-breaking influence such as a flux of optical photons. The recombination time for quasiparticles to form pairs is much greater than the characteristic time for their thermalization to the lattice temperature $T$. For this reason the model treats the unpaired electrons as a Fermi gas at temperature $T$, but more numerous than in the complete equilibrium situation.

• Received 28 February 1972

DOI:https://doi.org/10.1103/PhysRevLett.28.1559