Scanning Tunneling Spectroscopy of Proximity Superconductivity in Epitaxial Multilayer Graphene

TL;DR

This study investigates the spatial decay of proximity-induced superconductivity in epitaxial multilayer graphene using scanning tunneling spectroscopy, revealing a decay length over 400 nm and local deviations consistent with BCS theory.

Contribution

It provides the first spatially resolved measurements of proximity superconductivity decay in epitaxial graphene, demonstrating a decay length exceeding 400 nm and detailed local spectral variations.

Findings

Superconducting energy gap decays exponentially with distance from the interface.

Decay length of the superconducting gap exceeds 400 nm.

Local deviations from exponential decay occur on tens of nanometers.

Abstract

We report on spatial measurements of the superconducting proximity effect in epitaxial graphene induced by a graphene-superconductor interface. Superconducting aluminum films were grown on epitaxial multilayer graphene on SiC. The aluminum films were discontinuous with networks of trenches in the film morphology reaching down to exposed graphene terraces. Scanning tunneling spectra measured on the graphene terraces show a clear decay of the superconducting energy gap with increasing separation from the graphene-aluminum edges. The spectra were well described by Bardeen-Cooper-Schrieffer (BCS) theory. The decay length for the superconducting energy gap in graphene was determined to be greater than 400 nm. Deviations in the exponentially decaying energy gap were also observed on a much smaller length scale of tens of nanometers.