Coupling of cutoff modes in nonlinear lattices

The coupling of cutoff modes in nonlinear lattices is considered. It is shown that a novel class of lattice solitons is possible in the form of a coupled soliton-soliton or a coupled kink-soliton pair through a cross-phase modulation. Exact soliton solutions of coupled nonlinear amplitude equations for describing such a type of interacting nonlinear localized mode in lattices are presented and a macro-lattice experiment for their observation is suggested. Analytical results based on a quasi-discreteness approach are checked by numerical simulations.