Single molecule electronics is a field still in its infancy. Several exciting experiments have been performed in the last few years, but no clear answers have emerged to the fundamental question: what is the microscopic electronic description of a single molecule in contact with external leads? Single molecule electronics can be broken down two subfields, characterized by the terms "molecular wires" and "Coulomb blockade". Experiments on molecular wires are, at this point, all about understanding and optimizing molecule-lead contacts--a wire is only a wire if you can connect the ends cleanly to an external circuit. Molecular Coulomb blockade experiments start with the assumption of poor molecule-lead contact, and use electron tunneling onto and off of a molecule to learn something about the electronic states of the "isolated" molecule.
Both sides of single molecule electronics experiments will bring important new theoretical understanding, and new technological applications as well. At MIT most of our work has been focused on electromigration junctions, one of the few electrode geometries with gaps small enough to measure transport through single molecules. We found a surprising Kondo-type behavior in the junctions themselves, independent of any added molecules, and are investigating this further. At UBC we will develop more reliable metallic and semiconducting electrode systems for contacting single molecules, and use electrical detection to push electron and nuclear spin measurements to the single atomic scale.
