Josephson junctions in high-transition-temperature superconducting quantum interference devices

A superconducting quantum interference device (SQUID) is an extremely sensitive flux-to-voltage transducer with one or two Josephson junctions as its key elements. During the last two decades, high temperature superconducting Josephson junctions and even high-transition-temperature (high-Tc) SQUIDs have been fabricated from different kinds of high-transition-temperature superconducting cuprate materials. In particular, various types of high-temperature Josephson junctions, and even high-Tc SQUIDs of some practical value, have been fabricated from YBa2Cu3O7-δ (YBCO). This paper will mainly review the high-temperature Josephson junctions that have been used in high-Tc SQUIDs.