Quantum dc interference in YBa2Cu3O7-<i>x</i> ceramics at 77 K
Abstract
The Josephson effect 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 quantum interference observed earlier in multilinked samples of high-Tc superconducting ceramics and ac interference, there also exists a quantum interference in singly coupled samples of superconducting ceramics for direct current, the induction-voltage conversion steepness and the signal-to-noise ratio at 77 K being commensurate with similar characteristics of classical de SQUIDs operating at 4.2 K. It is found from the temperature dependence of the Josephson current in samples of size much larger than the coherence length that weak bonds in ceramics with percolation paths of current are of the S–N–S type.