Investigation of the energy gap of Y-Ba-Cu-O by point-contact Josephson-junction techniques

Abstract

Experimental results on stable point-contact Nb/Y-Ba-Cu-O structures are reported. Reproducible current-voltage characteristics showing Josephson coupling are obtained. Measurements of $\frac{\mathrm{dV}}{\mathrm{dI}}$ give an estimate for the energy-gap value of the high-${T}_{c}$ superconductor Y-Ba-Cu-O $\ensuremath{\Delta}=19.5\ifmmode\pm\else\textpm\fi{}2.0$ mV, corresponding to a ratio $[\frac{2\ensuremath{\Delta}(0)}{{k}_{B}{T}_{c}}]=4.8$ in agreement with previous results obtained by a different technique.