# Andreev reflection in ballistic normal metal/graphene/superconductor junctions

## TL;DR

This study investigates ballistic transport and Andreev reflection in graphene-based junctions, revealing how interface transparency and charge transfer influence superconducting behavior and electronic interference effects.

## Contribution

It introduces a modified Octavio-Tinkham-Blonder-Klapwijk model accounting for magnetic pair-breaking and interface transparency variations in graphene junctions.

## Key findings

- Charge carriers travel ballistically in the normal state.
- Superconducting Andreev reflection is affected by electronic interferences.
- Interface transparency varies with doping and influences transport properties.

## Abstract

We report the study of ballistic transport in normal metal/graphene/superconductor junctions in edge-contact geometry. While in the normal state, we have observed Fabry-P\'{e}rot resonances suggesting that charge carriers travel ballistically, the superconducting state shows that the Andreev reflection at the graphene/superconductor interface is affected by these interferences. Our experimental results in the superconducting state have been analyzed and explained with a modified Octavio-Tinkham-Blonder-Klapwijk model taking into account the magnetic pair-breaking effects and the two different interface transparencies, \textit{i.e.}\,between the normal metal and graphene, and between graphene and the superconductor. We show that the transparency of the normal metal/graphene interface strongly varies with doping at large scale, while it undergoes weaker changes at the graphene/superconductor interface. When a cavity is formed by the charge transfer occurring in the vicinity of the contacts, we see that the transmission probabilities follow the normal state conductance highlighting the interplay between the Andreev processes and the electronic interferometer.