Scanning tunneling spectroscopy of proximity superconductivity in epitaxial multilayer graphene

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.

Electrical Conductivity through a Single Atomic Step Measured with the Proximity-Induced Superconducting Pair Correlation

“…2(b)) that the DOS in the SIC layer just outside the edge of Pb islands is not uniform, which is in contrast with cases of flat metallic layers [8,11,13,14]. The site marked A, where the edge of the Pb island is directly situated on a terrace of the SIC phase, exhibits strong proximate effect, whereas at site B (C), where the edge of the island coincides with the upward (downward) step of the substrate, the proximate effect is intermediate and weak among the three sites (See Sec.…”

“…The propagation of the pair correlation from a superconductor / normal metal (SN) interface into the normal metal has been investigated by using STM/STS [8][9][10][11][12][13][14].…”

One-step synthesis of van der Waals heterostructures of graphene and two-dimensional superconducting α−Mo2C

“…heterostructures. The well-defined graphene/α-Mo2C vdW heterostructures provide an unprecedented platform to explore the proximity-induced 2D superconductivity by using scanning tunneling microscopy/spectroscopy (STM/STS) 32,39 . Figure 3a Fig.…”

Effects of Pb Intercalation on the Structural and Electronic Properties of Epitaxial Graphene on SiC

“…The graphene grown directly on superconducting Re(0001) substrate has been shown to exhibit superconducting behavior, as revealed by scanning tunneling microscopy (STM) tunneling spectroscopy . A superconducting proximity effect—which was induced by the presence of an aluminum film dispersed on epitaxial multilayer graphene on SiC—has also been explored very recently, and a superconducting order parameter with a coherence length of 400 nm was reported. In the particular case of Pb, recent studies on superconductivity in Pb films grown on Si(111) have demonstrated the occurrence of superconductivity in a single atomic layer, as well as in two atomic layer‐thick Pb films .…”