Electron transfer and vibrational modes in the finite molecular chain

A statistical quantum discrete model of a molecular bridge connecting metallic electrodes is proposed. A conductivity theory is developed on the assumption that the main contribution to electron transfer is made by non-equilibrium populated affinity states of a molecule. It is shown that both the field modification of molecular affinity states and the effect of Coulomb blockade lead to suppression of electron transfer. Relationships for different types of electron-vibron interaction in the chain are obtained. The current-voltage characteristics are calculated for different relative positions of the molecular spectrum and the electrodes' chemical potentials. Explanations for the step-like dependencies observed in the I-V characteristics and its asymmetry are provided. The phenomenon of molecular bridge half-integer and fractional charging is clarified.