Tunneling measurement of the energy gap in Y-Ba-Cu-O

Abstract

Superconductor-insulator-normal tunneling measurements have been performed on the high-$T_c$ superconductor ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{9\mathrm{-}\mathrm{\delta }}$ at 4.2 and 77 K. The results indicate an energy gap of magnitude 2${\Delta }_0$/$k_B$ $T_c$≊3.9 at T=0, with a temperature dependence consistent with the Bardeen-Cooper-Schrieffer theory of superconductivity.