Competition between the Superconducting Proximity Effect and Coulomb Interactions in a Graphene Andreev Interferometer

TL;DR

This study explores how electron-electron interactions in graphene influence the superconducting proximity effect, revealing a crossover in conductance oscillations linked to phase coherence changes, demonstrating graphene's utility for such investigations.

Contribution

It provides experimental evidence of the interplay between superconducting proximity effect and Coulomb interactions in graphene, highlighting the impact on phase coherence and conductance oscillations.

Findings

Crossover in Andreev conductance oscillations with gate voltage

High $V_{BG}$ behavior matches non-interacting electron predictions

Low $V_{BG}$ behavior shows interaction effects reducing phase coherence

Abstract

We have investigated transport through graphene Andreev interferometers exhibiting reentrance of the superconducting proximity effect. We observed a crossover in the Andreev conductance oscillations as a function of gate voltage ($V_{BG}$). At high $V_{BG}$ the energy-dependent oscillation amplitude exhibits a scaling predicted for non-interacting electrons, which breaks down at low $V_{BG}$. The phenomenon is a manifestation of electron-electron interactions, whose main effect is to shorten the single-particle phase coherence time $\tau_\phi$. These results indicate that graphene provides a useful experimental platform to investigate the competition between superconducting proximity effect and interactions.