ANOMALOUS TEMPERATURE EFFECT ON POINT-CONTACT Ag–LaBa2Cu3O7-x CONDUCTANCE SPECTRA

Abstract

The observation of an anomalous temperature behavior of the differential conductance versus voltage curves in contacts formed by an Ag tip and a bulk ceramic LaBa2Cu3O7-x with Tc around 92 K is reported. For a wide range of temperatures from Tc to helium-liquid ones, we have found a crossover from curves typical for a pure conducting normal metal–superconductor interface up to Giaever tunneling characteristics with gap features shifted to high biases. We take into account the existence of a degraded interlayer with suppressed superconducting parameters between a normal injector and a superconducting bulk and interpret qualitatively the data in terms of mesoscopic proximity effects. We argue that as the temperature is decreased, (i) the electron localization in a disordered region is enhanced, and (ii) in the interlayer, inelastic scattering processes become more effective. The latter was considered as a result of the inelastic scattering rate changes for charge carriers interacting with magnetic excitations in the near-interface region of high-Tc compound junctions.