Conditions for Bound States in a Superconductor with a Magnetic Impurity. II

Abstract

The binding energy of the localized excitation at a magnetic impurity $\mathrm{JS}·\sigma$ in a superconductor is plotted as a function of $J$. Our previous work is improved by including nonsingular terms in the solution to Suhl's scattering equations. These are found to alter the criteria for bound states significantly. The theory predicts that bound states deep in the gap will only occur for negative $J$ of the order of magnitude of the superconducting coupling constant $g$. For $J$ outside this range, any bound states will be very close to the gap edge, and the Abrikosov-Gor'kov theory should be satisfactory.