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.

Even a hundred years after its discovery, superconductivity continues to bring us new surprises, from superconducting magnets used in MRI to quantum detectors in electronics. 100 Years of Superconductivity presents a comprehensive collection of topics on nearly all the subdisciplines of superconductivity. Tracing the historical developments in supe

Superconductivity is a phenomenon occurring in certain materials at extremely low temperatures, characterized by exactly zero electrical resistance and the exclusion of the interior magnetic field (the Meissner effect). The electrical resistivity of a metallic conductor decreases gradually as the temperature is lowered. However, in ordinary conductors such as copper and silver, impurities and other defects impose a lower limit. Even near absolute zero a real sample of copper shows a non-zero resistance. The resistance of a superconductor, on the other hand, drops abruptly to zero when the material is cooled below its "critical temperature", typically 20 kelvin or less. An electrical current flowing in a loop of superconducting wire can persist indefinitely with no power source. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon. It cannot be understood simply as the idealisation of "perfect conductivity" in classical physics. Superconductivity occurs in a wide variety of materials, including simple elements like tin and aluminium, various metallic alloys and some heavily-doped semiconductors. Superconductivity does not occur in noble metals like gold and silver, nor in most ferromagnetic metals. In 1986 the discovery of a family of cuprate-perovskite ceramic materials known as high-temperature superconductors, with critical temperatures in excess of 90 kelvin, spurred renewed interest and research in superconductivity for several reasons. As a topic of pure research, these materials represented a new phenomenon not explained by the current theory. And, because the superconducting state persists up to more manageable temperatures, more commercial applications are feasible, especially if materials with even higher critical temperatures could be discovered. This new book presents leading research from around the world in this dynamic field.

Since the discovery of high temperature superconductors, many new materials have been invented. In the last year, several new materials were also discovered, but their critical temperatures are still below lOOK. Precise physical and chemical work has made tremendous progress in the theoretical and experimental study of physical properties and carrier state characterizations. The de Haas van Alphen effect measurement showed the existence of a Fermi surface in YBCO. Flux dynamics is a well-known new problem in which flux creep and irreversibility line features are especially important for a fundamental understanding of the critical current and flux pinning. Flux pinning centers which are intentionally added using non-superconducting precipitates, neutrons, and protons, etc. increase critical currents to practical levels. The analysis of electric and magnetic properties are expected to reveal the pinning mechanism and also to further application development. As for wires and bulks, many melt-like sintering techniques have improved the material performance of critical current densities. A new seeding Quench-Melt Growth technique enlarged crystal size and increased the repulsion force. These melting processes, in conjunction with a mechanical strength improvement have been effectively introduced into wire fabrication in order to realize kilometer range wires and will put the oxide wires to practical use. Where thin film is con cerned, when many fabrication methods had been developed using the assistance effect of activated oxygen such as ozone and oxygen radicals, a high current 2 density of 106A/cm at 77K was reported.

Intense recent activity in the field of high-temperature superconductivity both in Japan and in the rest of the world was discussed at the First International Symposium on Superconductivity held in Nagoya in August 1988. Current research and development efforts by major Japanese companies in the field of high-temperature superconductivity are reported by leading company scientists, to give an overview of the high level of activity in the area. Progress in the development of new materials and recent theoretical work is reported both from Japanese and international researchers. Contributions are organized by topic, with such topics as crystal chemistry and electronic structure, processing and microstructure, tapes and thick films, wires and coils, and thin film processing and properties. Future applications of superconductivity including magnetic levitation vehicles, electronics based on Josephson junctions, power delivery, energy storage, ship propulsion and magnetic resonance imaging are particularly stressed.

Five years have passed since the breakthrough in the critical temperature for superconductors. During this period, many superconducting materials have been discovered and developed, and our knowledge of the physical and other properties of oxide superconductors has deepened through extensive and intensive research. This knowledge has advanced superconductivity science and technology from the initial questioning stage to a more developed but still uncertain second stage where research activity in superconductivity now overlaps with fields of application. Generally speaking, science resonates with technology. Science not only complements but also competes with or stimulates technology. New scientific knowledge has triggered the second technological research stage. Much progress has been made in the development of practical devices, encouraging the application of superconductors in areas such as human levitation, a high speed levitated bearing, large current transforming leads, and high frequency devices. This technological progress has increased our understanding of the science involved, such as flux pinning and dynamics, and anomalous long-range superconducting interactions. At this important stage, international cooperation and collaborative projects can effectively sustain aggressive research and development in order to advance superconductivity to the next stages. The ISS Symposium is expected to serve as a venue for increasing our knowledge of superconductivity and for exchanging visions for future research and applications, through the presentation and discus of the latest research results. These proceedings also aim to summarize sion annual progress in high-Tc superconductivity in all fields.

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.