d-Wave YBCO dc superconductive quantum interference devices (dc SQUIDs)

Book chapter, 2011

The discovery of High Critical Temperature Superconductors (HTS) generated great activity to develop dc Superconductive Quantum Interference Devices (SQUIDs), with operating temperatures up to the boiling point of liquid nitrogen, 77. K.It was immediately apparent that small-scale devices, like SQUIDs, would require the development of thin-film techniques and novel Josephson junction's fabrication technologies. At present, grain-boundary junctions are the most widely used in SQUIDs. However, their properties are strongly affected by the d-wave symmetry of the order parameter. As a consequence the static and dynamic properties of HTS SQUIDs can be profoundly modified. The d-wave symmetry also offers the possibility to design π-SQUIDs showing a complementary behavior in magnetic field, compared to conventional ones, as well as dc SQUIDs with a double well potential. In this chapter the new Josephson phenomenology of HTS SQUIDs is derived, compared with experimental data available in literature, and discussed in view of future novel applications.