Zero-conductance resonances due to flux states in nanographite ribbon junctions

Electronic transport properties through junctions in nanographite ribbons a re investigated using the Landauer approach. In the low-energy regime ribbo ns with zigzag boundary have a single conducting channel of edge states. Th e conductance as a function of the chemical potential shows a rich structur e with sharp dips of zero conductance. Each zero-conductance resonance is c onnected with a resonant state which can be interpreted as the superpositio n of two degenerate flux states with Kekule-like current patterns; These ze ro-conductance dips are connected with a pronounced negative magnetoresista nce.