Superconducting Gap Renomalization around two Magnetic Impurities: From Shiba to Andreev Bound States

Tobias Meng, Jelena Klinovaja, Silas Hoffman, Pascal Simon, Daniel Loss

Published 2015-01-30Version 1

We study the renormalization of the gap of an s-wave superconductor in the presence of two magnetic impurities. For weakly bound Shiba states, we analytically calculate the part of the gap renormalization that is sensitive to the relative orientation of the two impurity spins. For strongly exchange coupled impurities, a quantum phase transition from a sub-gap Shiba state to a supra-gap Andreev state is identified and discussed by solving the gap equation self-consistently by numerics.