Spin - boson description of electron transmission through a molecular wire q

A spin-boson model based on local pseudo-spins acting in the electronic occupation number space is suggested and used to describe the thermally activated interelectrode current through a molecular wire. Utilizing the density matrix technique a unified description is achieved of all those kinetic processes which contribute to the inelastic current formation. These processes cover a specific superexchange transition between the terminal wire units as well as all sequential transitions leading from a given wire unit to the neighboring one. The exact solution of the kinetic equations is applied to a detailed analysis of the wire-length dependence of the current. The behavior differs between the sequential and the superexchange transfer mechanism and is discussed for a fixed electric field-strength in the wire as well as for a fixed applied voltage.