Tunable Klein-like tunneling of high-temperature superconducting pairs into graphene

TL;DR

This paper demonstrates a gate-tunable high-temperature superconducting proximity effect in graphene, revealing a novel Klein-like tunneling mechanism for superconducting pairs and enabling potential high-temperature Josephson devices.

Contribution

It introduces the first observation of high-temperature superconducting proximity effect in graphene with gate-tunable Klein-like tunneling of pairs, expanding the scope of superconducting electronics.

Findings

Superconducting pairs can tunnel through energy barriers via Klein tunneling.

Gating modulates supercurrent through quantum interference in graphene.

High-temperature proximity effect observed without ultra-clean graphene.

Abstract

Superconductivity can be induced in a normal material via the leakage of superconducting pairs of charge carriers from an adjacent superconductor. This so-called proximity effect is markedly influenced by graphene unique electronic structure, both in fundamental and technologically relevant ways. These include an unconventional form of the leakage mechanism the Andreev reflection and the potential of supercurrent modulation through electrical gating. Despite the interest of high-temperature superconductors in that context, realizations have been exclusively based on low-temperature ones. Here we demonstrate gate-tunable, high-temperature superconducting proximity effect in graphene. Notably, gating effects result from the perfect transmission of superconducting pairs across an energy barrier -a form of Klein tunneling, up to now observed only for non-superconducting carriers- and quantum interferences controlled by graphene doping. Interestingly, we find that this type of interferences become dominant without the need of ultra-clean graphene, in stark contrast to the case of low-temperature superconductors. These results pave the way to a new class of tunable, high-temperature Josephson devices based on large-scale graphene.