Transmission of electrons through a linear molecule : role of delocalized and localized electronic states in current formation

Exact formulas are obtained for the electronic current in the presence of quasielastic and elastic transmission of an electron through a molecule. The elastic transmission mechanism is analyzed in detail. It is shown that “metallization” of a molecule occurs in the presence of electron delocalization, so that all energy levels of the molecule undergo the same shift when a potential difference is established between the electrodes. This explains the appearance of resonance peaks in the conductivity of the molecule. When an electron in the molecule is strongly localized the appearance of conductivity peaks is due to resonance hopping of the electron between the Fermi levels of the electrodes and localized levels of the molecule, with which the appearance of negative conductivity of the molecule is also associated.