The Effect of Magnetic Impurities on the Response of Superconducting Photon Detectors

In a superconductor with magnetic impurities, scattering of conduction electrons results in the formation of localized states inside the superconducting gap. We show that inelastic electronic transitions involving quasiparticle scattering into and out of the localized states result in significant changes in the non equilibrium properties of the superconductor. The individual processes are: quasiparticle trapping into discrete states, enhanced recombination with localized quasiparticles, and pair breaking and de-trapping of localized quasiparticles by sub-gap phonons. We find that all these processes give rise to clearly distinguishable temperature dependences of the kinetic parameters indicating a possible role of magnetic scattering on the response of a photon detector.