The influence of non-magnetic impurity on collective oscillations in multiband superconducting systems

We investigate how non-magnetic chaotic distributed impurity influences on the collective oscillations in two-band superconductors. The usual two-band superconductors and the superconductors with redused carrier concentration (in the cases of phonon mechanism od superconductivity, respectively) will be researched. From the poles appearance condition for the vertex dunction the equation for frequency of collective oscillations and its sollution are obtained. The sollution depends on impurity as well as on the superconductor type (usual or exotic)