Effects of interlayer interactions on the critical temperature of high-Tc compounds

We show that the dependence of Tc on the number of layers in the unit cell of high-Tc Thallium compounds is quantitatively explained within the BCS framework, irrespective of the precise mechanism responsible for pairing. The intraplanar pairing is augmented by a weak interplanar scattering of the pair, thereby enhancing the Tc of layered compounds without increasing either the density of states or the number of carriers per CuO2 plane. The origin of the interplanar coupling is investigated and implications of the present model to other high-Tc materials (bismuth and yttrium compounds) are discussed.