Localization of excitations in a layered structure with interfaces characterized by a nonlinear response

The features of localization of excitations in a three-layer structure in which linear media are separated by boundaries with their own nonlinear response have been examined. It is shown that in the three-layer structure under consideration, localized states of two types can exist that differ in the distribution of the field in the inner layer, as well as in the frequency range of existence. Dispersion relations have been obtained that determine the energy dependence on system parameters in each case. The damping factors of surface waves are obtained in an explicit form. The conditions of the field localization are specified, depending on the characteristics of the layers and their interfaces. The energies of localized states have been found that do not exist in a symmetric structure without a wave interacting with the interfaces of the layers. Moreover, the presence of a nonlinear response of the boundaries is mandatory. It is shown that the interaction of a wave with the interfaces of the layers can lead to the absence of a localized state in a one-dimensional symmetric potential well with infinitely high walls and a nonlinear response. The influence of the media parameters and their interfaces on the flux carried by surface waves has been analyzed.