PHYSICS AND TECHNOLOGY OF HIGH-TEMPERATURE SUPERCONDUCTING JOSEPHSON-JUNCTIONS

The controllable fabrication of reliable HTS Josephson junctions with sufficiently small spread of their characteristic parameters has not y et been achieved and prevents the successful use of HTS Josephson junc tions in complex integrated circuits. The problems in HTS junction fab rication certainly are related to the specific properties of the cupra te superconductors, which make the fabrication of high quality interfa ces in HTS junctions employing artificial barrier layers extremely dif ficult. Therefore, several types of HTS Josephson junctions make use o f so-called intrinsic interfaces originating from grain boundaries or the intrinsic layer structure of the cuprates. Beyond the fabrication technology, the physics of HTS Josephson junctions is not well underst ood. In particular, the detailed mechanisms of charge transport in the various junctions types and the impact of an unconventional symmetry of the superconducting order parameter are unsettled issues. We summar ize the key issues regarding the physics and technology of HTS Josephs on junctions and discuss possible routes to a useful HTS junction tech nology.