Origin of conductance quantization in disordered graphene ribbons

TL;DR

This study uses numerical simulations to explain the unexpected conductance quantization in disordered graphene nanoribbons, showing that defect-induced backscattering near subband edges causes equally spaced conductance plateaus even at low conductance levels.

Contribution

It provides a quantitative explanation for conductance quantization in disordered graphene ribbons, linking defect scattering to conductance plateaus.

Findings

Conductance plateaus occur at low conductance levels due to defect scattering.

Backscattering near subband edges enhances conductance quantization.

Results explain experimental observations of conductance quantization in disordered ribbons.

Abstract

We present numerical studies of conduction in graphene nanoribbons with different types of disorder. We find that even when defect scattering depresses the conductance to values two orders of magnitude lower than 2e^2/h, equally spaced conductance plateaus occur at moderately low temperatures due to enhanced electron backscattering near subband edge energies if bulk vacancies are present in the ribbon. This work accounts quantitatively for the surprising conductance quantization observed by Lin et al. [Phys. Rev. B 78, 161409 (2008)] in ribbons with such low conductances.