Soliton dynamics and Peierls-Nabarro barrier in a discrete molecular chain

We investigate the motion of a self-localized quasiparticle in a discrete lattice taking into account the interaction of the quasiparticle with the vibrations of the lattice. Using an original method to control the velocity of solitonlike excitations in a discrete system, the dependence of their velocity, momentum, and energy on the carrying wave vector is analyzed. The velocity of the solitonlike excitations is found to saturate at wave vectors below those predicted by continuum models. This is as found in experimental observations. Also, the properties of the Peierls-Nabarro relief, caused by the lattice discreteness, and pinning of a soliton by this barrier, are studied. The influence of the initial condition on the Peierls-Nabarro barrier and soliton motion is investigated. For low-width solitons, a critical value of the wave vector is needed to overcome the Peierls-Nabarro barrier. ©2000 The American Physical Society.