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The modified superexchange model is used to derive the expression for nonresonant tunneling conductance mediated by localized and delocalized molecular orbitals associated with the terminal and the interior molecular units respectively. The model is shown to work as long as delocalization of electron density in the chains molecular orbitals is sustained during the tunneling. The criteria for reduction of the superexchange model of charge tunneling to the flat barrier model are formulated and the parameters of the barrier model (energy gap and effective electron mass) are specified in the terms of inter-site coupling and energy distance from the Fermi level to the delocalized wires HOMO level. Application of the theory tothe experiment shows that the modified superexchange model is quite appropriate to explain the experimental results in case of the nonresonance tunneling conductance in --(CH$_2)$$_N$--NH$_2$ and HOOC--(CH$_2)$$_N$--COOH molecular wires.
We study the conductance threshold of clean nearly straight quantum wires in the magnetic field. As a quantitative example we solve exactly the scattering problem for two-electrons in a wire with planar geometry and a weak bulge. From the scattering
We study the conductance of a quantum wire in the presence of weak electron-electron scattering. In a sufficiently long wire the scattering leads to full equilibration of the electron distribution function in the frame moving with the electric curren
Quasi-ballistic semiconductor quantum wires are exposed to localized perpendicular magnetic fields, also known as magnetic barriers. Pronounced, reproducible conductance fluctuations as a function of the magnetic barrier amplitude are observed. The f
The contact conductance between graphene and two quantum wires which serve as the leads to connect graphene and electron reservoirs is theoretically studied. Our investigation indicates that the contact conductance depends sensitively on the graphene
Superconducting wires with broken time-reversal and spin-rotational symmetries can exhibit two distinct topological gapped phases and host bound Majorana states at the phase boundaries. When the wire is tuned to the transition between these two phase