Plasma Resonance in Layered Normal Metals and Superconductors
  A microscopic theory of the plasma resonance in layered metals is presented. It is shown that electron-impurity scattering can suppress the plasma resonance in the normal state and sharpen it in the superconducting state. Analytic properties of the conductivity for the electronic transport perpendicular to the layers are investigated. The dissipative part of the electromagnetic response in c-direction has been found to depend on frequency in a highly non-trivial manner. This sort of behavior cannot be incorporated in the widely used phenomenological Gorter-Kazimir model. 
S.V. Pokrovsky and V.L.Pokrovsky