Paramagnetic impurities in strong coupling superconductors

Abstract

We have calculated the effect of paramagnetic impurities on strong coupling superconductors. Imaginary axis solutions of the Eliashberg gap equations with a spin-flip term form the basis of our work. We compute the variation of the critical temperature ($T_c$) with increasing impurity concentration, the functional derivatives of $T_c$, the specific-heat jump, the critical-field deviation function, and the tunneling characteristics which we compare with the results of Abrikosov-Gor'kov theory. In all cases important strong coupling corrections are obtained.