K-space gap anisotropy within the interlayer pair-tunneling mechanism of high-T-c superconductivity

We consider a mean-field approach to a 2D extended Hubbard model for a bilayer superconductor, in presence of coherent interlayer pair-tunneling and quenched coherent single particle tunneling. The functional form of the intralayer pairing potential is dictated by the symmetry character of the underlying crystal lattice. This gives rise to a competition between s- and d-wave symmetry, as the chemical potential is increased from the bottom to the top of a, realistic band for most cuprates. It allows for mixed-symmetry paired state at temperatures below T-c, but never at T-c on a square lattice. The interlayer pair-tunneling mechanism contributes to the pairing potential as an effective k-diagonal term, which is responsible of a nonconventional k-dependence of the gap function. We study the evolution of such a gap structure with temperature and with band filling.