Shot Noise in Lithographically Patterned Graphene Nanoribbons

TL;DR

This study measures shot noise and conductance in graphene nanoribbons at very low temperatures, revealing disorder effects and Coulomb gap phenomena near charge neutrality.

Contribution

It provides the first detailed shot noise analysis of lithographically patterned graphene nanoribbons, linking noise characteristics to disorder and Coulomb interactions.

Findings

Fano factor approximately 0.4 away from charge neutrality

Fano factor increases to about 0.7 near charge neutrality

Results align with models of disordered graphene with strong scattering

Abstract

We have investigated shot noise and conductance of multi-terminal graphene nanoribbon devices at temperatures down to 50 mK. Away from the charge neutrality point, we find a Fano factor $F \approx 0.4$, nearly independent of the charge density. Our shot noise results are consistent with theoretical models for disordered graphene ribbons with a dimensionless scattering strength $K_0 \approx 10$ corresponding to rather strong disorder. Close to charge neutrality, an increase in $F$ up to $\sim 0.7$ is found, which indicates the presence of a dominant Coulomb gap possibly due to a single quantum dot in the transport gap.