Magnetic pair breaking in disordered superconducting films

A theory for the effects of nonmagnetic disorder on the magnetic pair-breaking rate α induced by paramagnetic impurities in quasi-two-dimensional superconductors is presented. Within the framework of a strong-coupling theory for disordered superconductors, we find that the disorder dependence of α is determined by the disorder enhancements of both the electron-phonon coupling and the spin-flip scattering rate. These two effects have a tendency to cancel each other. With parameter values appropriate for ${\mathrm{Pb}}_{0.9}$${\mathrm{Bi}}_{0.1}$, we find a pair-breaking rate that is very weakly dependent on disorder for sheet resistances 0<${\mathit{R}}_{\mathrm{\square }}$≲2.5 kΩ, in agreement with a recent experiment by Chervenak and Valles. © 1996 The American Physical Society.