On the relation between the presence of the resonance and the type of the spectrum rearrangement in a disordered system

Abstract

Using a model one-dimensional system, we demonstrate that the single-impurity resonance mode does not always result in a normal cross-type spectrum, rearrangement when the impurity concentration increases. A substitutional impurity strongly bound to the rigid substrate produces a resonance in the optical phonon branch. The subsequent spectrum rearrangement, however, is of an anomalous type, creating a smooth dispersion curve in the vicinity of the resonance frequency instead of a distinctive quasi-gap characteristic of the cross-type.