Superconducting gap, normal state pseudogap, and tunneling spectra of bosonic and cuprate superconductors

We develop a theory of normal metal–superconductor and superconductor tunneling in “bosonic” superconductors with strong attractive correlations taking into account coherence effects in single-particle excitation spectrum and disorder. The theory accounts for the existence of two energy scales, their temperature and doping dependencies, asymmetry, and inhomogeneity of tunneling spectra of underdoped cuprate superconductors