Dissipation in molecular junctions.

A recently developed theory that formulates the phenomena of inelastic transport and current-driven dynamics in molecular-scale electronics within a time-dependent scattering approach is extended to account for dissipation of the current-induced excitation through coupling to electrode phonons and electron-hole pairs. Our approach treats the electronic transport, the nuclear dynamics, and the energy and phase exchange between the electronic and the vibrational subspaces in the course of the inelastic scattering event within the Schrodinger picture, whereas the dissipation of the energy deposited in the nuclear modes is accounted for within a density matrix approach. Subsequent to formulation of the theory in terms of population relaxation and phase decoherence rates, we develop approaches for computing these rates, treating on equal footing the dissipation due to excitation of electron-hole pairs and that due to the interaction with phonons. Finally, we test the derived rates by application to the model problem of CO adsorbed on metal surfaces, an example that has been extensively studied previously and for which several experimental results are available for comparison.