Importance of grain-boundary Josephson junctions in the electron-doped infinite-layer cuprate superconductor Sr1−xLaxCuO2

Abstract

Grain-boundary bicrystal Josephson junctions of the electron-doped infinite-layer superconductor Sr1−xLaxCuO2 (x=0.15) were grown by pulsed laser deposition. BaTiO3-buffered 24∘ [001]-tilt symmetric SrTiO3 bicrystals were used as substrates. We examined both Cooper pair (CP) and quasiparticle (QP) tunneling by electric transport measurements at temperatures down to 4.2K. CP tunneling revealed an extraordinary high critical current density for electron-doped cuprates of jc>103 A/cm2 at 4.2 K. Thermally activated phase slippage was observed as a dissipative mechanism close to the transition temperature. Out-of-plane magnetic fields H revealed a remarkably regular Fraunhofer-like jc(H) pattern as well as Fiske and flux-flow resonances, both yielding a Swihart velocity of 3.1×106 m/s. Furthermore, we examined the superconducting gap by means of QP tunneling spectroscopy. The gap was found to be V shaped with an extrapolated zero-temperature energy gap Δ0≈2.4 meV. No zero-bias conductance peak was observed.

Source-reported materials — not catalogue approval

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