The authors of this book present current research in the study of superconductivity. Topics discussed in this compilation include the effects of non-magnetic defects in hole doped cuprates; deep cryogenic refrigeration by photons based on the phonon deficit effect in superconductors; superconductivity driven by an anti-polar electric phase in high temperature superconducting materials; superconductive graphite intercalation compounds; a superconducting magnetic field concentrator with nanodimensional branches and slits; magnetic mechanisms of pairing in a strongly correlated electron system of copper oxides; two non-linear mechanisms of correlations between copper carriers in superconductivity and their microscopical descriptions; three dimensionality of the critical state and variational methods for magnetically anisotropic superconductors; theory of multi-band superconductivity; conserving approximation for the self-energy of the t-U-V-J model beyond the Hartree-Fock approximation; and superconductivity as a consequence of an ordering of zero-point oscillations in electron gas.

Superconductivity is the ability of certain materials to conduct electrical current with no resistance and extremely low losses. High temperature superconductors, such as La2-xSrxCuOx (Tc=40K) and YBa2Cu3O7-x (Tc=90K), were discovered in 1987 and have been actively studied since. In spite of an intense world-wide research, a complete understanding of the copper oxide (cuprate) materials is still lacking. Many fundamental questions are unanswered, particularly the mechanism by which high-Tc superconductivity occurs. More broadly, the cuprates are in a class of solids with strong electron-electron interactions. An understanding of such 'strongly correlated' solids is perhaps the major unsolved problem of condensed matter physics with over ten thousand researchers working on this topic. High-Tc superconductors also have significant potential for applications in technologies ranging from electric power generation and transmission to digital electronics. This ability to carry large amounts of current can be applied to electric power devices such as motors and generators, and to electricity transmission in power lines. For example, superconductors can carry as much as 100 times the amount of electricity of ordinary copper or aluminium wires of the same size. This Publication presents new research on yttrium barium copper oxide superconductors, often abbreviated YBCO, which is a chemical compound with the formula YBa2Cu3O7. This material, a famous 'high-temperature superconductor', achieved prominence because it was the first material to superconduct above the boiling point of nitrogen. All materials developed before YBCO became superconducting only at temperatures near the boiling points of liquid helium or liquid hydrogen (Tb = 20.1 K). The significance of the discovery of YBCO is the breakthrough in the refrigerant used to cool the material to below the critical temperature.

Superconductivity is the ability of certain materials to conduct electrical current with no resistance and extremely low losses. High temperature superconductors, such as La2-xSrxCuOx (Tc=40K) and YBa2Cu3O7-x (Tc=90K), were discovered in 1987 and have been actively studied since. In spite of an intense, world-wide, research effort during this time, a complete understanding of the copper oxide (cuprate) materials is still lacking. Many fundamental questions are unanswered, particularly the mechanism by which high-Tc superconductivity occurs. More broadly, the cuprates are in a class of solids with strong electron-electron interactions. An understanding of such "strongly correlated" solids is perhaps the major unsolved problem of condensed matter physics with over ten thousand researchers working on this topic. High-Tc superconductors also have significant potential for applications in technologies ranging from electric power generation and transmission to digital electronics. This ability to carry large amounts of current can be applied to electric power devices such as motors and generators, and to electricity transmission in power lines. For example, superconductors can carry as much as 100 times the amount of electricity of ordinary copper or aluminium wires of the same size. Many universities, research institutes and companies are working to develop high-Tc superconductivity applications and considerable progress has been made. This volume brings together new leading-edge research in the field.

The 12th International Symposium on Superconductivity was held in Morioka, Japan, October 17-19, 1999. Convened annually since 1988, the symposium covers the whole field of superconductivity from fundamental physics and chemistry to a variety of applications. At the 12th Symposium, a mini-symposium focusing on the two-dimensionality of high-temperature superconductors, or the c-axis transport, and a session on vortex physics were organized. There were also many reports on the recent developments of YBCO-based coated conductors both in the United States and in Japan, AC losses of wires and tapes, developments of bulk materials with strong flux pinning, the recent progress in thin film and junction technologies, and the demonstration of various electronics applications using SQUIDs, microwave devices, and single-flux-quantum (SFQ) digital devices. This volume is a valuable resource for all those working in the field of superconductivity.

More than seven years have passed since the dramatic breakthrough in the critical temperature for superconductors. During this period, a host of new materials have been discovered, and efforts have been stepped up in a variety of domains including device and systems applications, commercialization, and basic research on the properties of superconductive materials. Recent progress in areas such as bulk single crystal production, long-scale wire and tape produc tion, flywheel and bearing applications, and electronic device applications for thin films indicate that science and technology have been working hand in hand in this field, as has been the case in the research and development of semi conductors. This interdisciplinary "resonance" will be certain to lead to further outstanding advances in the years to come. It goes without saying that worldwide information exchange is the key to accelerating progress in superconductivity science and technology. As in previous years, the ISS '93 served as a venue where visions of future develop ments were shared in addition to presentations and extensive discussions on the most up-to-date research results. I hope that the Proceedings contained in this volume will be consulted not only as a summary of the current "state of the art" in high-Tc superconductivity but also as a stimulating source of ideas regarding future applications of superconductivity research.

In contrast to research on the fundamental mechanisms of High-Temperature Superconductivity, in recent years we have seen enormous developments in the fabrication and application of High-Tc-superconductors. The two volumes of High Temperature Superconductivity provide a survey of the state of the technology and engineering applications of these materials. They comprise extended original research papers and technical review articles written by physicists, chemists, materials scientists and engineers, all of them noted experts in their fields. The interdisciplinary and strictly application-oriented coverage should benefit graduate students and academic researchers in the mentioned areas as well as industrial experts. Volume 1 "Materials" focuses on major technical advancements in High-Tc materials processing for applications. Volume 2 "Engineering Applications" covers numerous application areas where High-Tc superconductors are making tremendous impact.

The International Symposium on Superconductivity, which has been held annu ally since 1988, is a forum for presenting the most up-to-date information about a broad range of research and development in superconductivity, from funda mental aspects to applications. More than 10 years have passed since the discovery of oxide superconductors and since various developments of applications began. It may be said that the prospects for application of oxide superconductors recently have opened up. Great progress has been made toward practical use, for example, of the flywheel, which uses bulk materials, and the high-performance cryo-cooled magnet made of bismuth wire. These were the results of persistent efforts to develop materials from the viewpoint of materials science and engineering. Also important is the progress in comprehensive understanding of high temperature superconductivity. Unique electronic properties of cuprates such as the non-Fermi liquid normal state, spin-charge separation, spin gap, and d-wave symmetry were discussed at the symposium, as were the unique electromagnetic properties resulting from the low dimensionality of cuprates. In the field of new superconductors, many exotic materials have been discovered since 1986. A decade of work with cuprate superconductors is reviewed in this proceedings, and several of the newest materials are presented. These papers will be instructive for many researchers and for students who are to enter this field.