Formulation of charge transport in molecular junctions with time-dependent molecule-leads coupling operators.

The problem of time-dependent molecule-leads coupling in single-molecule junctions is acute for the structure, stability and functionality of these systems during non-equilibrium transport. Time-dependence of molecule-lead coupling operators may rise when they are perturbed directly, or formally (indirectly), when time-dependent perturbation to the molecule or to the leads are mapped onto the coupling operators by unitary transformations. In this work a reduced density matrix formulation is outlined for the study of transport in the presence of time-dependent couplings. The formulation assumes weak molecule-lead coupling, but accounts for many body interactions within the molecule, and for strong time-dependent field. For band limited or periodic fields the formulation leads to kinetic equations which map the time-dependent transport problem onto a static transport problem with multiple leads, thus providing convenient working equations as well as a useful tool for interpreting experiments on field driven single molecule junctions. Applications to concrete models are demonstrated. [ABSTRACT FROM AUTHOR]