INTERACTION OF DISCRETE BREATHERS WITH IMPURITY MODES

We study the interaction between a discrete breather and an impurity in a nonlinear lattice model. Although the existence of the breather is due to nonlinearity while the existence of an impurity mode is due to a mass inhomogeneity, the two modes are very similar and therefore interact strongly. Their interaction provides some insight on the interplay between nonlinearity and disorder which localize energy in a lattice. In particular we show that an impurity can act as a catalyst for the fusion of two breathers and the generation of a larger excitation.