Scattering theory approach to inelastic transport in nanoscale systems

We present a scattering-state description for the nonequilibrium multichannel charge transport in the presence of electron-vibration couplings. It is based on an expansion of scattering orders of eigenchannel states. Examining charge transitions between scattering states, we clarify competing inelastic and elastic scattering processes and compare with the interpretation based on the nonequilibrium Green's functions formalism. We also derive a general expression for conductance variations in single-channel systems that provides a comprehensive picture for the variation, including the well-known result, the 0.5 rule, from the aspect of interplay between elastic and inelastic scattering processes.