Directed transport of the davydov solitons by unbiased a.c. forces

Abstract

We show that in asymmetric molecular chains a periodic unbiased field causes a drift of the Davydov solitons. This directed current, known as ratchet phenomenon, has a threshold with respect to the intensity and the frequency of the field. In spatially symmetric chains a harmonic periodic electric field generates oscillations of solitons but does not result in their directed drift. Such a drift current can be induced in symmetric chains by a time periodic asymmetric external field. This complex dynamics of solitons is generated by the interplay between the Peierls-Nabarro barrier, external field and dissipative effects in the chain. The dependence of the amplitude of soliton oscillations and the velocity of the drift are shown to depend on the intensity of the field, its frequency and the coefficient of the energy dissipation. © 2009 Springer Science + Business Media B.V.