The role of solitons in charge and energy transfer in 1D molecular chains

Abstract

The idea that polarons and solitons could play the crucial role in the transport processes in biological structures, has been critically reexamined on the basis of the general theory of self-trapping phenomena. The criteria which enable one to determine conditions for the existence and stability of polarons and solitons and to determine their character, in dependence of the values of the basic physical parameters of the system, were formulated. Validity of the so-called Davydovs soliton model was discussed on the basis of these criteria. It was found that the original Davydovs proposal, based upon the idea of the soliton creation due to the single excitation (particle, vibron, etc.) self-trapping, cannot explain the intramolecular energy transfer in ct-helix and acetanilide. However, Davydov theory is flexible enough to describe the single electron transfer in some systems (alpha-helix and acetanilide for example). In the many-particle systems, dressing effect due to the quantum nature of phonons, may cause the creation of the bound states of the several excitons in the molecular chain, The possibility of creation of the soliton states of this type is discussed for the simple Frohlichs one-dimensional model. The regions of;he system parameter space where different mechanisms dominate the behaviour of such entities are characterized, Copyright (C) 1998 Elsevier Science B.V.