DENSITY OF STATES AND TUNNELING SPECTRA IN 2-DIMENSIONAL D-WAVE SUPERCONDUCTORS

The quasiparticle density of states is discussed in the framework of d-wave superconductivity, and the corresponding superconductor-insulator-superconductor tunneling conductivity sigma(V) is obtained. We find a quadratic increase of sigma(V) at low voltage and two maxima at higher voltage. These features are in qualitative agreement with recent experimental findings of Forro et al. An s-wave state also gives rise to a double-peak structure, but no quadratic low-voltage behavior is found.