Low-energy electronic collective modes and superconductivity in layered systems

The Coulomb interaction induces low-energy electronic collective modes (LEE CM) in layered conductors. We study how the superconducting critical temper ature T-c is affected by such collective modes within the strong-coupling t heory of superconductivity. Whereas we account for both the electron-phonon and the screened Coulomb interactions, the main focus is set on the latter . The dielectric function is displayed and screening within RPA is discusse d. We then show that LEECM affect the superconducting state constructively in layered structures. Their effect can be interpreted as a negative mu* in the Eliashberg theory. We examine in what respect the collective-mode scen ario differs in layered conductors as compared to three-dimensional (3D) is otropic metals.