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 ${p}_{\mathrm{Au}}\ensuremath{\sim}60%$. 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.