Nonlinear transport through ultra-narrow zigzag graphene nanoribbons: non-equilibrium charge and bond currents

The electronic nonlinear transport through ultra-narrow graphene nanoribbons (sub-10 nm) was studied. A stable region of negative differential resistance (NDR) appears in the I–V characteristic curve of odd zigzag graphene nanoribbons (ZGNRs) at both positive and negative polarity. This NDR originates from a transport gap induced by a selection rule that blocks the electron transition between disconnected energy bands of ZGNR. Based on this transition rule, the on/off ratio of the current increases exponentially with ribbon length up to 10⁵. In addition, charging effects and the spatial distribution of bond currents were studied by using the non-equilibrium Green's function formalism in the presence of electron–electron interaction at a mean-field level. We also performed an ab initio density functional theory calculation of the transmission through a passivated graphene nanoribbon to demonstrate the robustness of the transport gap against hydrogen termination of the zigzag edges.