Nonlinear conductance quantization in graphene ribbons

TL;DR

This paper numerically investigates nonlinear conductance in graphene nanoribbons, revealing asymmetries in conductance quantization due to scattering and potential pinning, explaining experimental observations.

Contribution

It introduces a detailed numerical analysis of nonlinear conductance in graphene ribbons, highlighting the effects of scattering and potential pinning on conductance quantization.

Findings

Asymmetry in conductance plateaus between electron and hole branches.

Strong defect scattering restores symmetry and explains upward shifts.

Potential pinning at the drain or source influences conductance behavior.

Abstract

We present numerical studies of non-linear conduction in graphene nanoribbons when a bias potential is applied between the source and drain electrodes. We find that the conductance quantization plateaus show asymmetry between the electron and hole branches if the potential in the ribbon equals the source or drain electrode potential and strong electron (hole) scattering occurs. The scattering may be at the ends of a uniform ballistic ribbon connecting wider regions of graphene or may be due to defects in the ribbon. We argue that, in ribbons with strong defect scattering, the ribbon potential is pinned to that of the drain (source) for electron (hole) transport. In this case symmetry between electron and hole transport is restored and our calculations explain the upward shift of the conductance plateaus with increasing bias that was observed experimentally by Lin et al. [Phys. Rev. B 78, 161409 (2008)].