Andreev reflection in Graphene–superconductor junctions in the quantum Hall regime*

We investigate the Andreev reflection at an interface between a graphene layer in the quantum Hall regime and a superconductor. In graphene due to the spin and valley degrees of freedom there is an approximate SU(4) symmetry. The breaking of this symmetry due to interactions and the Zeeman effect leads to a splitting of the Landau levels. In this talk I will discuss the effect on the Andreev reflection of the breaking of the Landau levels' spin and valley degeneracy. I will then show results for the Andreev reflection amplitude, and the Andreev reflection contribution to the interface conductance, for various degrees of transparency of the interface.