Hubbard model approach for the transport properties of short molecular chains

Transport properties of short molecular chains connecting metallic electrodes are studied within the one-band Hubbard model taking into account electron Coulomb interactions in the self-consistent (Hartree-Fock) approximation. The current-voltage characteristics are represented as a sequence of the voltage ranges differing in the number of channels dominating in the electron transport. These channels originate from the molecular self-consistent energy (SCE) levels trapped in the source-drain voltage window. The new qualitative effect of the electron repulsion is the pinning of the SCE levels by the Fermi energy of the source or the drain lead throughout the finite voltage ranges. The computed current-voltage curves are in a good qualitative agreement with the experimental data. For the case of the two-atom device and the weak coupling between the leads and the molecule, the analytical solution for the charge and the current is obtained.