We have realized an integer quantum Hall system with superconducting contacts by connecting graphene to niobium electrodes. Below their upper critical field of 4 tesla, an integer quantum Hall effect coexists with superconductivity in the leads, but with a plateau conductance that is larger than in the normal state. We ascribe this enhanced quantum Hall plateau conductance to Andreev processes at the graphene-superconductor interface leading to the formation of so-called Andreev edge-states. The enhancement depends strongly on the filling-factor, and is less pronounced on the first plateau, due to the special nature of the zero energy Landau level in monolayer graphene.
@article{arxiv.1303.3394,
title = {Quantum Hall effect in graphene with superconducting electrodes},
author = {Peter Rickhaus and Markus Weiss and Laurent Marot and Christian Schönenberger},
journal= {arXiv preprint arXiv:1303.3394},
year = {2013}
}