One common strategy to generate topological superconductivity and Majorana modes in condensed matter is through the coupling of an s-wave superconductor to a helical half-metallic system. Despite promising progress on a number of appealing implementations based on this idea (such as proximitized semiconductors or topological insulators with strong spin-orbit coupling), a clear demonstration of topological superconductivity remains, to date, an experimental challenge.
After a pedagogical introduction, I will discuss a novel approach to obtain topological superconductivity and Majorana states in graphene-superconductor junctions [1]. Key to our proposal is the interaction-induced magnetic ordering of graphene’s zero Landau level [2] . Coupling this unique state to an s-wave superconductor gives rise to novel edge states whose properties depend on the type of magnetic order. In particular, the canted antiferromagnetic phase is a natural host for Majorana bound states. Remarkable experimental progress has recently been reported in the proposed type of junctions [3], which offers a promising outlook for Majorana physics in graphene systems.
[1] P. San Jose, J. L. Lado, R. Aguado, F. Guinea, and J. Fernández-Rossier, PHYSICAL REVIEW X 5, 041042 (2015).
[2] A. F. Young, et al, Nature (London) 505, 528 (2014)
[3] M. Ben Shalom, et al, Nature Physics 14, 12 (2015); V. E. Calado, et al, Nat. Nanotechnol. 10, 761 (2015); F. Amet, et al, arXiv1512.09