Zero-Conductance Resonances due to Flux States in Nanographite Ribbon Junctions

The electronic transport properties through junctions in nanographite ribbons are investigated using the Landauer approach. In the low-energy regime ribbons with zigzag boundary have a single conducting channel of edge states. The conductance as a function of the chemical potential shows a rich structure with sharp dips of zero conductance. Each zero-conductance resonance is connected with a resonant state which can be interpreted as the superposition of two degenerate flux states with Kekul\'e-like current patterns. These zero-conductance dips are connected with a pronounced negative magneto resistance.