Visualizing landscapes of the superconducting gap in heterogeneous superconductor thin films: geometric influences on proximity effects

TL;DR

This study investigates how the geometry of heterostructures influences the spatial propagation of the superconducting gap, revealing geometry-dependent local and non-local proximity effects in 2D superconductor-metal systems.

Contribution

It provides new insights into the geometric control of proximity effects in heterogeneous superconducting systems, highlighting the role of local geometry on superconducting gap distribution.

Findings

Superconducting gap confinement varies with junction geometry.

Non-local proximity effects can extend the gap over many coherence lengths.

Geometry influences the spatial profile of the superconducting order parameter.

Abstract

The proximity effect is a central feature of superconducting junctions as it underlies many important applications in devices and can be exploited in the design of new systems with novel quantum functionality. Recently, exotic proximity effects have been observed in various systems, such as superconductor-metallic nanowires and graphene-superconductor structures. However, it is still not clear how superconducting order propagates spatially in a heterogeneous superconductor system. Here we report intriguing influences of junction geometry on the proximity effect for a 2D heterogeneous superconductor system comprised of 2D superconducting islands on top of a surface metal. Depending on the local geometry, the superconducting gap induced in the surface metal region can either be confined to the boundary of the superconductor, in which the gap decays within a short distance (~ 15 nm), or can be observed nearly uniformly over a distance of many coherence lengths due to non-local proximity effects.