Bond dissociation and correlation effects in molecular electronic devices.

We present a simple model for a fundamental process in molecular electronics: The change in conductance upon bond breaking. In our model, a diatomic molecule is attached to spin-polarized contacts. Employing a Hubbard Hamiltonian, electron interaction is explicitly considered in the molecule and neglected in the contacts, enabling us to study the impact of electron interaction on the molecular conductance. In the limit where the electron repulsion is strong compared to the binding energy (as is the case upon dissociation), electron transmission is strongly suppressed compared to the noninteracting case. On the other hand, the spin-polarized contacts introduce a coupling between the molecular singlet and triplet states, as a consequence of which the energy gap between the lowest resonances is reduced.