Electrical conductance of zigzag nanographite ribbons with locally applied gate voltage

The electric conductance of the graphite ribbon with locally applied gate voltage has been studied in terms of the Landauer approach. In the low-energy region, nano-graphite ribbon with zigzag boundaries exhibits the single electronic transport channel due to the edge states. The chemical potential dependence of the electric conductance shows qualitatively different behavior, depending on whether the magnitude of the potential barrier (gate voltage bias) V-g is larger than the energy gap Delta of the single channel region of the zigzag ribbon. For positive V-g with V-g < Delta, the zero-conductance resonances appear for 0 less than or equal to E less than or equal to V-g, and average transmission probability is quite small in this region. However the transmission probability is almost one, i.e. perfect transmission, for E > V-g. This step-function-like behavior of the conductance shows that it is possible to fabricate a nano-graphite-based switching device by the application of weak gate voltage bias.