Electronic Transport through Molecular Junctions with Non-Rigid Molecule-Leads Coupling
Written by Maytal Caspary Toroker
The Schulich Faculty of Chemistry and The Lise Meitner Center for Computational Quantum Chemistry, Technion – Israel Institute of Technology, Haifa 32000, Israel
The conventional approach to the calculation of the current through a molecular size conductor is based on the Landauer formalism, which considers the transmission along a single electronic scattering coordinate. The Landauer formalism was recently extended by Troisi, Ratner and Nitzan to include nuclear degrees of freedom of the molecule, and the effects of electronic-nuclear coupling within the molecule were shown to result in inelastic contributions to the current. However, electronic-nuclear coupling outside the molecular subspace, associated with a dependence of the molecule-leads coupling terms on the nuclear coordinates was not accounted for explicitly. In this work we generalize the formulation of inelastic transport to the case of electronic-nuclear coupling which is external to the molecular conductor. Although this electronic-nuclear coupling is external to the molecule there is no need to extend the molecular subspace when projection operators are employed for calculations of the current through the junction. A test case of a conductor with vibrating contacts to the leads is studied numerically. It is demonstrated that contact vibrations lead to inelastic contributions to the current and to characteristic features in the I-V curve and its derivatives, similar to the ones observed for internal (molecular) electronic-nuclear coupling.
Reference: M. Caspary Toroker, U. Peskin. J. Chem. Phys. (2007), in press.