We combine scanning-tunneling-spectroscopy experiments probing magnetic impurities on a superconducting surface with a theoretical analysis of the tunneling processes between (superconducting) tip and substrate. We show that the current is carried by single-electron tunneling at large tip-substrate distances and Andreev reflections at smaller distances. The single-electron current requires relaxation processes between the impurity-induced Shiba bound state and the quasiparticle continuum, allowing us to extract information on such relaxation processes from our analysis.
@article{arxiv.1502.05048,
title = {Tunneling processes into localized subgap states in superconductors},
author = {Michael Ruby and Falko Pientka and Yang Peng and Felix von Oppen and Benjamin W. Heinrich and Katharina J. Franke},
journal= {arXiv preprint arXiv:1502.05048},
year = {2015}
}