Planar tunneling along EuS nanowire edge junctions formed over Au(111) for topological superconductivity

Metallic surface states, such as those in Au(111), with strong Rashba spin-orbit coupling and induced superconductivity could host topological superconductivity when coupled to the nanostructures of magnetic insulators, for example EuS [1,2]. Following our prior work [1], we report our progress on fabricating scalable EuS nanowires coupled to Au(111) surface. We further fabricate planar tunneling devices with highly transparent junctions at the ends of the EuS nanowires and carry out local tunneling spectroscopy down to milli-Kelvin temperatures. The transparent junctions allow us to resolve the sub-gap states with finer energy resolution, and the evolution of the sub-gap states under an applied planar magnetic field. We will discuss our studies on the sub-gap states including the zero bias conductance peak, in particular those features that are limited by thermal broadening. We will further discuss the connections between our results and topological superconductivity.

[1] PNAS 117, 8775, (2020); [2] Phys. Rev. Res. 3, 043086, (2021)