Interplay between band structure and gap symmetry in a two-dimensional anisotropic superconductor

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Abstract
We consider the two-dimensional quasiparticle density of states and superconductor-insulator-superconductor (SIS) tunneling conductance, σ(V), using a BCS-like framework for a gap function exhibiting the symmetries of an unspecified off-site pairing interaction. For d-wave pairing, we find the usual nodal structure in the gap function. In addition, one can also find nodal structure at the Fermi surface for a gap function with extended s-wave symmetry (but only when hopping beyond near neighbors is considered). This is a universal feature arising solely due to the interplay between the Fermi-surface geometry and the momentum variation of the gap function and leads to unique signatures in the SIS tunneling spectra.