SPATIOTEMPORAL BEHAVIOR IN A PHI(4) MODEL OF LATTICE-DYNAMICS

A simple phenomenological model of lattice dynamics in ferroelectric m aterials has the ingredients of a spatially extended, nonlinear driven system. We study the dynamics of this model in the presence of spatia lly varying ultrafast optical pulses. We find that for sufficiently la rge amplitudes, the spatial gradient in the pulse creates stable domai n walls separating domains of opposite orientations. The dynamics of t hese domain walls under repeated pulses is investigated. Bifurcation d iagrams in one, two, and three dimensions are obtained, exhibiting bot h periodic and complex spatiotemporal behavior. The complex behavior i s identified as weakly chaotic associated with algebraic growth of ini tial small perturbations.