Quantum transport in honeycomb lattice ribbons with zigzag edges

We explore electron transport properties in honeycomb lattice ribbons with zigzag edges coupled to two semi-infinite one-dimensional metallic electrodes. The calculations are based on the tight-binding model and the Green’s function method, which numerically compute the conductance-energy and current-voltage characteristics as functions of the lengths and widths of the ribbons. Our numerical results predict that for such a ribbon an energy gap always appears in the conductance spectrum across the energy E = 0. With the increase of the size of the ribbon, the gap gradually decreases but it never vanishes. This clearly manifests that a honeycomb lattice ribbon with zigzag edges always exhibits the semiconducting behavior, and it becomes much more clearly visible from our presented current-voltage characteristics. PACS No.: 73.63.-b; 73.63.Rt.