Effects of anisotropy on the critical temperature in layered nonadiabatic superconductors

The generalized anisotropic Eliashberg theory is employed to study the critical temperature of layered nonadiabatic superconductors where the relevant phonon energy is comparable to the Fermi energy. We consider a two-dimensional model appropriate for cuprate compounds and recently discovered superconductor magnesium-diboride (MgB2) which also reveals layered structure. By using the McMillan approximation we present the result of calculations of critical temperature Tc. It is shown that the critical temperature is enhanced due to the influence of anisotropy and nonadiabaticity.