A tunneling spectroscopy study of the pairing symmetry in the electron-dopedPr1−xLaCexCuO4−y

Abstract

We have performed scanning tunneling spectroscopy and point contactspectroscopy measurements on the electron-doped superconductorPr1−xLaCexCuO4−y (x = 0.12, K). We address the question of the symmetry of the order parameter andof the amplitude of the energy gap. We compare three possible scenarios,i.e. isotropic s-wave, ‘anisotropic’ s-wave, and d-wave. Evidence for a d-wavesymmetry of the order parameter is given. From the temperature evolution of thedI/dV versusV characteristics we extract a BCS-like temperature dependence of the superconducting energy gapΔ. Despitethe variety of measured spectra we give a consistent explanation for the whole set of data, indicatingΔ = (3.6 ± 0.2) meV and a ratio . In particular, point contact characteristics showing gap-like features at higher voltageshave been interpreted by considering the formation of an intergrain Josephson junction inseries with the point contact junction. Further confirmation of the correctness of themodel is given by the behavior of the critical current of the intergrain Josephsonjunction versus temperature which follows the Ambegaokar–Baratoff behavior.