Conductance manipulation at the molecular level

Using a tight-binding model we have studied the electronic transmission through a C₆₀ molecule sandwiched between a metal surface and a metal (scanning tunnelling microscope) tip. By simulating compression of C₆₀ we have interpreted an experimental study of the variation of the conductance through a C₆₀ molecule with an applied external pressure. We found that the observed increase in conductance cannot be explained in terms of the changes in the electronic structure of the C₆₀ molecule alone. Effects related to the metal/molecule contact, i.e. the strength of the metal/C₆₀ interaction and the shape of the molecular orbitals in the tip, are in fact more important for the conductance. In view of this we discuss the importance of interference effects in the tip/molecule coupling.