Local modes and localization in a multicomponent nonlinear lattice

The existence, stability, and the conditions for the formation of nonlinear localized modes are investigated in a two-component one-dimensional lattice. In spite of their possible coupling with acoustic phonons, discrete breathers can exist as exact stable solutions or show a very slow decay. Nonlinear energy localization through energy exchange between localized excitations, exhibited previously for a one-component lattice [T. Dauxois and M. Peyrard, Phys. Rev. Lett. 70, 3935 (1993)] is more general and also valid in a multicomponent lattice. A self-localization of thermal fluctuations is also observed in such a system. The model is used to investigate the effect of bending proteins on DNA. It shows that a bend can collect the energy of moving localized modes or insulate one part of the molecule from transfers of energy from large amplitude excitations in other parts.