Superconductivity enhanced conductance fluctuations in few layer graphene nanoribbons

Abstract

We investigate the mesoscopic disorder induced rms conductance variance $\delta G$ in a few layer graphene nanoribbon (FGNR) contacted by two superconducting (S) Ti/Al contacts. By sweeping the back-gate voltage, we observe pronounced conductance fluctuations superimposed on a linear background of the two terminal conductance G. The linear gate-voltage induced response can be modeled by a set of inter-layer and intra-layer capacitances. $\delta G$ depends on temperature T and source-drain voltage $V_{sd}$. $\delta G$ increases with decreasing T and $|V_{sd}|$. When lowering $|V_{sd}|$, a pronounced cross-over at a voltage corresponding to the superconducting energy gap $\Delta$ is observed. For $|V_{sd}|\ltequiv Δ$ the fluctuations are markedly enhanced. Expressed in the conductance variance $G_{GS}$ of one graphene-superconducutor (G-S) interface, values of 0.58 e^2/h are obtained at the base temperature of 230 mK. The conductance variance in the sub-gap region are larger by up to a factor of 1.4-1.8 compared to the normal state. The observed strong enhancement is due to phase coherent charge transfer caused by Andreev reflection at the nanoribbon-superconductor interface.

15 pages, 5 figures

References in corpus (11)

• Electric Field Effect in Atomically Thin Carbon Films
• Graphene: Status and Prospects
• Suspended Graphene: a bridge to the Dirac point
• Intrinsic and Extrinsic Performance Limits of Graphene Devices on SiO2
• Bipolar supercurrent in graphene
• Strong suppression of weak (anti)localization in graphene
• Quantum-limited shot noise in graphene
• Josephson Current and Multiple Andreev Reflections in Graphene SNS Junctions
• Gauge field induced by ripples in graphene
• Tuning the proximity effect in a superconductor-graphene-superconductor junction
• Andreev reflection versus Coulomb blockade in hybrid semiconductor nanowire devices

Cited by in corpus (3)

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• Conductance fluctuations in graphene devices with superconducting contacts in different charge density regimes