Topological Aspects of Charge-Carrier Transmission across Grain Boundaries in Graphene

Dislocations and grain boundaries
are intrinsic topological defects
of large-scale polycrystalline samples of graphene. These structural
irregularities have been shown to strongly affect electronic transport
in this material. Here, we report a systematic investigation of the
transmission of charge carriers across the grain-boundary defects
in polycrystalline graphene by means of the Landauer-Büttiker
formalism within the tight-binding approximation. Calculations reveal
a strong suppression of transmission at low energies upon decreasing
the density of dislocations with the smallest Burgers vector b = (1,0). The observed transport anomaly is explained from
the point of view of resonant backscattering due to localized states
of topological origin. These states are related to the gauge field
associated with all dislocations characterized by b =
(n,m) with n – m ≠
3q (q ∈ Z). Our work identifies an
important source of charge-carrier scattering caused by the topological
defects present in large-area graphene samples produced by chemical
vapor deposition.