Conductance manipulation at the molecular level

Using a tight-binding model we have studied the electronic transmission through a C-60 molecule sandwiched between a metal surface and a metal (scanning tunnelling microscope) tip. By simulating compression of C-60 we have interpreted an experimental study of the variation of the conductance through a C-60 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 C-60 molecule alone. Effects related to the metal/molecule contact, i.e. the strength of the metal/C-60 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.