Undoped cuprate superconductors — band superconductors or oxygen-doped Mott-Hubbard superconductors?

Eliashberg analysis of the optical conductivity in superconducting Pr2CuOx with x ≃ 4

Superconducting Pr(2)CuO(x), x ≃ 4 films with T' structure and a T(c) of 27 K have been investigated by millimeter-wave transmission and broadband (infrared-to-ultraviolet) reflectivity measurements in the normal and superconducting state. The results obtained by both experimental methods show a consistent picture of the superconducting condensate formation below T(c). An Eliashberg analysis of the data proves d-wave superconductivity and unitary-limit impurity scattering of the charge carriers below T(c). The derived electron-exchange boson interaction spectral function I(2)χ(ω) shows only marginal changes at the superconducting transition with the mass enhancement factor λ, the first inverse moment of I(2)χ(ω), being equal to 4.16 at 30 K and to 4.25 at 4 K.