Solitonic energy transfer in a coupled exciton-vibron system

We consider the exciton transfer along a one-dimensional molecular chain. The exciton motion is influenced by longitudinal vibrations evolving in a Toda lattice potential. It is shown how the soliton solutions of the vibron system coupled to the exciton system induce solitonic exciton transfer. To this aim the existence of a regime of suppressed energy exchange between the coupled excitonic and vibrational degrees of freedom is established in the case of which a nonlinear Schrodinger equation for the exciton variable is derived. The nonlinear Schrodinger equation possesses soliton solutions corresponding to coherent transfer of the localized exciton.