Electron Transmission through Aromatic Molecules

A prominent feature of aromatic compounds is the ring current that can be observed indirectly in nuclear magnetic resonance experiments. This current is generated by an external magnetic field. In molecular electronics, molecules serve as conductors, and they are connected to metallic contacts that act as electron sources and electron sinks. We show that ring currents can also be found in molecular electronic devices containing cyclic π-electron systems. The circular currents are related to interference phenomena that can render the molecule impenetrable to electrons. While only small currents pass through the molecule, large internal circular currents are stimulated. We conjecture that the internal currents should result in experimentally observable magnetic moments.