Electrical transport through single-molecule junctions: from molecular orbitals to conduction channels.

We present an atomistic theory of electronic transport through single organic molecules that reproduces the important features of the current-voltage ( I-V) characteristics observed in recent experiments. We trace these features to their origin in the electronic structure of the molecules and their local atomic environment. We demonstrate how conduction channels arise from the molecular orbitals and elucidate the contributions of individual orbitals to the current. We find that in thiol-bridged aromatic molecules many molecular orbitals contribute to a single conduction channel and discuss the implications of this result for the design of molecular devices.