Nonequilibrium transport properties for a three‐site quantum wire model

We derive nonequilibrium electronic transport properties for a three‐site quantum wire model within Hartree‐Fock approximation making use of Keldysh formalism. Some rigorous formulas are provided for direct calculations when Coulomb repulsion is present. According to numerical calculations using these formulas, we investigate the conductance, transport current, and on site electronic charges of the wire in some special occasions. In noninteracting case, when site‐site couplings in the wire are tougher than wire‐electrode couplings, the resonant tunneling transport takes place and the phenomenon of conductance quantization can be easily observed. The transport properties of up‐spin are identical with those of down‐spin. When the Coulomb interaction is present, the line shapes of transport characteristics are changed because of electron‐electron repulsions. With the increase of U, the Coulomb blockade and metal‐insulator transition (Mott transition) phenomena are obvious if the self‐energies Γ have small values compared with U. The transport properties of the up‐spin also become quite different from those of the down‐spin indicating that the spin polarization takes place in the wire. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)