Quantum interference at direct current in ceramics YBa2Cu3O7-x

The Josephson effects and quantum dc interference in superconducting ceramics YBa2Cu3O7-x having the superconducting transition temperature of 93 K are investigated experimentally. It is shown that along with the known quantum interference, observed in multilink samples of high-Tc superconducting ceramics and ac interference, in the superconducting ceramics there exists quantum interference which also occurs in one-coupled samples at direct current, the induction-voltage conversion steepness and the signal-noise ratio in the high-Tc superconducting ceramics at 77 K being commensurate with similar charateristics of classical dc squids operating at 4.2 K. It is found from the temperature dependence of the Josephson current in samples whose sizes are much greater than coherence lengths, that links in the ceramics with percolation paths of current flow refer to the SNS type percolation paths of current flow refer to the SNS type