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 pair ing Delta(parallel to) of d(x)2(-y)2 symmetry. This model is motivated by a recent photoemission experiment reporting the splitting of the n odes of the energy gap. In addition to offering a natural explanation of this observation, the model has a number of new experimental conseq uences We find that the new state is accompanied by a spontaneous brea king of the tetragonal symmetry. We also find that the out-of-phase os cillation of Delta(perpendicular to) and Delta(parallel to) gives rise to a new Raman active mode. The phase of Delta(perpendicular to) may also become imaginary, leading to a state which breaks time reversal s ymmetry, which may have important implications for tunnelling experime nts.