  Electronic transport in a model molecular device coupled to local phonon
modes is theoretically analyzed. The method allows for obtaining an accurate
approximation of the system's quantum state irrespective of the electron and
phonon energy scales. Nonlinear electrical features emerge from the calculated
current-voltage characteristics. The quantum corrections with respect to the
adiabatic limit characterize the transport scenario, and the polaronic
reduction of the effective device-lead coupling plays a fundamental role in the
unusual electrical features.
