Edge state transport through disordered graphene nanoribbons in the quantum Hall regime

TL;DR

This study investigates how disordered graphene nanoribbons exhibit quantum Hall effects and phase coherent scattering, revealing that transport gaps persist in high magnetic fields and fluctuations are due to disorder-induced scattering.

Contribution

It provides experimental evidence of quantum Hall plateaux and phase coherent scattering in disordered graphene nanoribbons, highlighting the role of disorder in transport properties.

Findings

Quantum Hall plateaux observed at high magnetic fields.

Transport gap persists in the quantum Hall regime.

Reproducible fluctuations linked to phase coherent scattering.

Abstract

The presence of strong disorder in graphene nanoribbons yields low-mobility diffusive transport at high charge densities, whereas a transport gap occurs at low densities. Here, we investigate the longitudinal and transverse magnetoresistance of a narrow (60 nm) nanoribbon in a six-terminal Hall bar geometry. At B= 11 T, quantum Hall plateaux appear at $\sigma_{xy}=\pm2e^2/h$, $\pm6e^2/h$ and $\pm10e^2/h$, for which the Landau level spacing is larger than the Landau level broadening. Interestingly, the transport gap does not disappear in the quantum Hall regime, when the zero-energy Landau level is present at the charge neutrality point, implying that it cannot originate from a lateral confinement gap. At high charge densities, the longitudinal and Hall resistance exhibit reproducible fluctuations, which are most pronounced at the transition regions between Hall plateaux. Bias-dependent measurements strongly indicate that these fluctuations can be attributed to phase coherent scattering in the disordered ribbon.