Abstract
The T-dependent conductance G(V,T) of evaporated Pb junctions on cleaved ab planes of (2:2:1:2) crystals is presented. Strong superconducting (V,T) structures imply a large gap, approximately (0)=26 meV, or 2(0)/=6.7. An analysis of G(V,T) near , assuming a lifetime-broadened BCS (E), reveals a broadening Γ(T) such that Δ()≊Γ()≊2. The fitted Δ(), unlike typical BCS values, is ≊0.8Δ(0). $G(V,T>T sub c )— has a minimum at V=0, suggestive of known c-direction localization in 2:2:1:2 compounds. G(V,T) also reveals the expected fluctuation superconductivity above . 4.2-K scanning-tunneling-microscope (STM) spectra are mentioned in comparison. A larger gap, about 40 meV, and dip at 80 meV, found in the STM G(V) are tentatively attributed to planes.
- Received 26 November 1991
DOI:https://doi.org/10.1103/PhysRevB.45.10622
©1992 American Physical Society