The transport properties in a normal-conductor-superconductor (NS) junction are investigated when a magnetic impurity is present in the normal region. As the spin of quasiparticles is reversed when they are Andreev-reflected from the NS interface, spin-flip scattering takes place regardless the spin alignment of an incident quasiparticle with respect to the magnetic impurity. The magnetic coupling between the quasiparticle and the impurity gives rise to subgap conductance peaks. The resonance state responsible for the subgap structures is found to be a hybrid of singlet and triplet states.
Takagaki, Y., & Ploog, K. H. (2000). Subgap conductance structures of a normal-conductor-superconductor junction induced by a magnetic impurity. Physica E: Low-Dimensional Systems and Nanostructures, 8(1), 66–71. https://doi.org/10.1016/S1386-9477(00)00114-4