Single particle tunneling and photoemission spectra in anisotropic layered high-temperature superconductors

We explore the effects of an anisotropic order parameter on the single particle tunneling conductance and on angular integrated and angular resolved photoemission spectra. Adopting a tight-binding model band structure, extended s-wave pairing and the BCS strategy, we calculate the tunneling conductance for specular and diffuse transmission and the coherent part of the photoemission spectrum. Recent evidence for gap anisotropy, resulting from tunneling perpendicular and parallel to the layers, is traced back to x, y-anisotropy mediated by nearestneighbor intralayer pairing. This anisotropy is also found to be consistent with angular integrated photoemission measurements. It is shown that angular resolved photoemission experiments with high resolution would allow a more detailed identification of this anisotropic superconducting state. © 1990 Springer-Verlag.