Electron Transport In Graphene Nanoribbons Research Articles

Electron transport in graphene nanoribbons under a central potential modulation

We study electron transport in graphene nanoribbons (GNs) under a one-dimensional central potential. Two kinds of structures are considered: armchair-edged GN (AGN) where a central potential is applied on the central dimer chain, and zigzag-edged GN (ZGN) where a potential is applied on the central zigzag chain. Both nanoribbons show unique electronic structure and interesting transport properties under potential modulation. Without considering edge effect, a metallic AGN is still metallic after potential modulation. However, if the edge effect is considered, an AGN under potential modulation can be either semiconducting or metallic depending on the potential strength. The AGN transits from semiconducting to metallic and then to semiconducting again with the potential increase. As to ZGN, the potential on the central zigzag chain also greatly affect the quantum conductance. A ZGN will transit from metallic to semiconducting as the potential strength exceeds critical value. All transitions of AGN and ZGN are correlated with the localized state on the central potential chain which induces a quantum channel along the chain.

The effect of magnetic field and disorders on the electronic transport in graphenenanoribbons

We developed a unified mesoscopic transport model for graphene nanoribbons, whichcombines the nonequilibrium Green’s function (NEGF) formalism with the real-spaceπ-orbital model. Based on this model, we probe the spatial distribution of electrons under amagnetic field, in order to obtain insights into the various signature Hall effects indisordered armchair graphene nanoribbons (AGNR). In the presence of a uniformperpendicular magnetic field (-field), a perfect AGNR shows three distinct spatial current profiles at equilibrium,depending on its width. Under nonequilibrium conditions (i.e. in the presence of an appliedbias), the net electron flow is restricted to the edges and occurs in opposite directionsdepending on whether the Fermi level lies within the valence or conduction band.For electrons at an energy level below the conduction window, the -field gives rise to local electron flux circulation, although the global flux is zero. Our studyalso reveals the suppression of electron backscattering as a result of the edge transportwhich is induced by the -field. This phenomenon can potentially mitigate the undesired effects of disorder, such asbulk and edge vacancies, on the transport properties of AGNR. Lastly, we show that theeffect of -field on electronic transport is less significant in the multimode compared to thesingle-mode electron transport.

Transport in disordered graphene nanoribbons

We study electronic transport in graphene nanoribbons with rough edges. We first consider a model of weak disorder that corresponds to an armchair ribbon whose width randomly changes by a single unit cell size. We find that in this case, the low-temperature conductivity is governed by an effective one-dimensional hopping between segments of distinct band structure. We then provide numerical evidence and qualitative arguments that similar behavior also occurs in the limit of strong uncorrelated boundary disorder.

Quantum dynamics of electron in graphene nanoribbons with edge disorder

Considering both the finite size and the edge disorder, we explore the dynamic behavior of electrons in graphene nanoribbons (GNRs) with various geometries in terms of quantum diffusion theory. It is shown that in the regime of stronger disorder, the decay exponent δ and the diffusion exponent β increase with increasing edge disorder, while they decrease in the regime of weaker disorder. This indicates that there exists a localization–quasi-delocalization transition in GNRs upon varying the strength of edge disorder, similar to that in a shell-doped nanowire. In addition, the edge disorder has an influence of varying importance on the electronic transport in GNR, which depends on its width and edge geometry, showing up as a singular quantum size effect. The results can contribute towards understanding of the strange transport properties of graphene sheets and their potential applications.