Macroscopic-ranged proximity effect in graphite

Abstract

We report proximity-induced superconducting features over macroscopic lengths in highly oriented pyrolytic graphite. The phenomenon is triggered when electrical currents are injected in the material through superconducting electrodes, few millimeters apart from each other. Such a large range is anomalous, as proximity-induced features in normal conductors hardly surpass few micrometers. The results can be explained as due to the presence of pre-existing superconductivity in graphite on small, localized regions.

Anomalous superconducting proximity effect of planar Pb–RhPb2 heterojunctions in the clean limit

“…This agrees markedly with a selfconsistent solution of the Usadel equations 26,27 . On the other hand, LRP effects, which survive over scales largely exceeding the phase-coherence length of proximitized materials, have been unexpectedly evidenced in a large variety of systems and attracted increasing attention 25,[28][29][30][31][32][33][34] . This is because they not only shed light on the superconducting pairing mechanism but also help develop high-performance superconducting devices.…”

“…This is because they not only shed light on the superconducting pairing mechanism but also help develop high-performance superconducting devices. The underlying cause for the so-called LRP effects or giant proximity effects is phenomenally related to the properties of the proximitized materials that are either located in the ballistic regime (clean limit) with l > ξ 35 or characteristic of superconducting fluctuations 36 , or both 33 . From this point of view, planar heterojunctions between two dissimilar superconductors are likewise desired for spatially resolved spectroscopic studies and microscopic understanding of the unpredicted LRP effects.…”