ENERGY-GAP STRUCTURE IN BILAYER OXIDE SUPERCONDUCTORS

We consider a model for bilayer superconductors where an interlayer pa iring amplitude Delta(perpendicular to) coexists with intralayer pairi ng Delta(parallel to) of d(x2-y2) symmetry. This model is motivated by a recent photoemission experiment reporting the splitting of the node s of the energy gap. In addition to offering a natural explanation of this observation, the model has a number of new experimental consequen ces. We find that the new state is accompanied by a spontaneous breaki ng of the tetragonal symmetry. We also find that the out-of-phase osci llation of Delta(perpendicular to) and Delta(parallel to) gives rise t o a new Raman active mode. The phase of Delta(perpendicular to) may al so become imaginary, leading to a state which breaks time reversal sym metry, which may have important implications for tunnelling experiment s.