Breather mobility in discrete phi(4) nonlinear lattices

We introduce a systematic approach to investigate movability properties of localized excitations in discrete nonlinear lattice systems and apply it to phi 4 lattices. Starting from the anticontinuous limit, we construct localized breather solutions that are shown to be linearly stable and to possess a pinning mode in the double well case. We demonstrate that an appropriate perturbation of the pinning mode yields a systematic method for constructing moving breathers with a minimum shape alteration. We find that the breather mobility improves with lower mode frequency. We analyze properties of the breather motion and determine its effective mass.