Shot Noise in Lithographically Patterned Graphene Nanoribbons

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.