We have studied nonequilibrium phonon effects on the electric current and the energy current through atomic and molecular bridge junctions in terms of the Su-Schrieffer-Heeger model. Due to the inelastic coupling between electrons and phonons, the two currents are closely correlated. The correlation was taken into account in our theory where kinetic equations are solved not only for electrons but also for phonons. The offset behavior of the inelastic tunneling spectrum is successfully described by our theory. In addition to this, it was found that a vibronic energy current arises as a result of the inelastic coupling and a nonequilibrium phonon effect, similar to the phonon drag effect, even in isothermal conditions.

• Received 12 November 2007

DOI:https://doi.org/10.1103/PhysRevB.78.045434