Three-dimensional gap structure in layered high-temperature superconductors

NMR data and electromagnetic response are quantitatively described by a multiband-multiphonon exchange model, which additionally explains why near zeros in the superconducting gap function are shifted away from high symmetry points, as observed by angle-resolved photoemission spectroscopy measurements. The basic idea concentrates on the three-dimensionality of superconductivity, incorporating a coupling of the plane to the c axis via multiphonon exchange leading to a complex gap structure. Band structure related effects and chemistry are consistently included in this approach.