Scattering Theory Approach to Inelastic Transport in Nanoscale Systems

We present a scattering-state description for the non-equilibrium 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 clarifies competing inelastic and elastic scattering processes, and compare with the interpretation based on the non-equilibrium Green's functions formalism. We also derive a general expression for conductance variations in single-channel systems. It 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.