Electrical transport and superconductivity in a Au-YBa2Cu3O7 percolation system

Abstract

Percolation behaviors of normal-state conductivity and superconductivity have been studied in a Au-Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ granular system. The normal-state conductivity shows a percolation threshold at a Au volume fraction $p_{\mathrm{Au}}$ of 23%, whereas the superconducting network shows a threshold at $p_{\mathrm{Au}}\sim 60\%$. The presence of Au has negligible effect on the superconducting Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ phase. In the dilute limit, the ratio of the Meissner signal to the diamagnetic-shielding signal approaches unity.