ANOMALOUS TEMPERATURE EFFECT ON POINT-CONTACT Ag–LaBa₂Cu₃O_7-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 LaBa 2 Cu 3 O 7−x with Tc around 92 K is reported. For a wide range of temperatures from Tc to heliumliquid 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.

Inelastic electron tunneling across magnetically active interfaces in cuprate and manganite heterostructures modified by electromigration processes

“…In our previous paper [3] we presented tunneling measurements on hightemperature superconducting cuprates, another family of perovskites. It was shown that in these materials interactions of tunneling electrons with excitations inside the transitional insulating layer strongly influence the conductance spectra.…”

“…It was shown that in these materials interactions of tunneling electrons with excitations inside the transitional insulating layer strongly influence the conductance spectra. The system investigated experimentally [3] was a point-contact junction prepared with a sharp Ag tip pressed into the surface of a ceramic superconductor LaBa 2 Cu 3 O 7-x (LBCO). The latter one is known to be one of the most unstable materials among superconducting high-T c cuprates, with a bad degraded layer adjoining the surface.…”

“…The values of the Curie temperature agreed well with known data (the inset in Fig.1,a). Point-contact junctions were prepared with a silver counterelectrode by the same way as those based on high-T c LBCO compounds (for details see the paper [3]). The corresponding peak in the temperature dependence of the tunnel resistance for LCMO was always shifted to lower T as a result of the suppression of ferromagnetism in the upper layers of the manganites (the inset in Fig.1,a).…”