Subharmonic gap structure in short ballistic graphene junctions

TL;DR

This paper theoretically investigates the current-voltage behavior of short ballistic graphene SNS junctions, revealing a complex subharmonic gap structure modifiable by gate voltage, with conductance near the Dirac point resembling diffusive junctions.

Contribution

It provides a detailed theoretical analysis of subharmonic gap structures in short ballistic graphene SNS junctions, highlighting gate voltage effects and conductance behavior near the Dirac point.

Findings

Rich subharmonic gap structure modulated by gate voltage

Conductance near the Dirac point matches diffusive SNS junctions

Differential conductance exhibits complex features in the short-junction regime

Abstract

We present a theoretical analysis of the current-voltage characteristics of a ballistic superconductor-normal-superconductor (SNS) junction, in which a strip of graphene is coupled to two superconducting electrodes. We focus in the short-junction regime, where the length of the strip is much smaller than superconducting coherence length. We show that the differential conductance exhibits a very rich subharmonic gap structure which can be modulated by means of a gate voltage. On approaching the Dirac point the conductance normalized by the normal-state conductance is identical to that of a short diffusive SNS junction.