Role of Symmetry in the Transport Properties of Graphene Nanoribbons under Bias

TL;DR

This paper explores how the symmetry of zigzag graphene nanoribbons influences their electrical transport properties under bias, revealing that symmetry determines whether they conduct normally or exhibit conductance gaps.

Contribution

It demonstrates that the symmetry of ZGNRs critically affects their transport behavior, a novel insight into the role of symmetry in nanoscale conductance.

Findings

Symmetric ZGNRs show conductance gaps and very small currents.

Asymmetric ZGNRs behave as conventional conductors with linear I-V characteristics.

Transport differences are due to coupling variations between conducting subbands.

Abstract

The intrinsic transport properties of zigzag graphene nanoribbons (ZGNRs) are investigated using first principles calculations. It is found that although all ZGNRs have similar metallic band structure, they show distinctly different transport behaviors under bias voltages, depending on whether they are mirror symmetric with respect to the midplane between two edges. Asymmetric ZGNRs behave as conventional conductors with linear current-voltage dependence, while symmetric ZGNRs exhibit unexpected very small currents with the presence of a conductance gap around the Fermi level. This difference is revealed to arise from different coupling between the conducting subbands around the Fermi level, which is dependent on the symmetry of the systems.