Break-junction tunneling measurements of the high-Tc superconductor Y1Ba2Cu3O9−δ

Abstract

Current-voltage tunneling characteristics in a high-critical-temperature superconducting material containing predominately ${\mathrm{Y}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{9\mathrm{-}\mathrm{\delta }}$ have been measured using the break-junction technique. Sharp gap structure was observed, with the largest superconductive energy gap measured to be Δ=19.5±1 meV, assuming a superconductor-insulator-superconductor junction. This energy gap corresponds to 2Δ/$k_B$ $T_c$=4.8 at T=4 K, for a critical temperature of 93 K (midpoint of the resistive transition).