Impurity-induced stabilization of solitons in arrays of parametrically driven nonlinear oscillators

Chains of parametrically driven, damped pendula are known to support solito nlike clusters of in-phase motion which become unstable and seed spatiotemp oral chaos for sufficiently large driving amplitudes. We show that the pinn ing of the soliton on a "long" impurity (a longer pendulum) expands dramati cally its stability region, whereas "short" defects simply repel solitons p roducing an effective partition of the chain. We also show that defects may spontaneously nucleate solitons.