Evidence for Quasibound States in a Kondo Superconductor

Abstract

Contrary to the predictions of the Abrikosov-Gor'kov theory, it is found that a Kondo superconductor (Ce in La) is gapless even at very low concentrations and temperatures. At low impurity (Ce) concentrations in La, the number of states in the gap as determined from electron tunneling measurements is proportional to the Ce concentration. These states are likely to be quasibound states which result from electron scattering from the impurities.