The International Winter School on Electronic Properties of High-Temperature Superconductors, held between March 7-14, 1992, in Kirchberg, (Tyrol) Austria, was the sixth in a series of meetings to be held at this venue. Four of the earlier meetings were dedicated to issues in the field of conducting polymers, while the winter school held in 1990 was devoted to the new discipline of high-T c superconductivity. This year's meeting constituted a forum not only for the large number of scientists engaged in high-Tc research, but also for those involved in the new and exciting field of fullerenes. Many of the issues raised during the earlier winter schools on conducting polymers, and the last one on high-T c superconductivity, have taken on a new significance in the light of the discovery of superconducting C materials. 60 The Kirchberg meetings are organized in the style of a school where expe rienced scientists from universities, research laboratories and industry have the opportunity to discuss their most recent results, and where students and young scientists can learn about the present status of research and applications from some of the most eminent workers in their field. In common with the previous winter school on high-Tc superconductors, the of the cuprate superconductors. present one focused on the electronic properties In addition, consideration was given to related compounds which are relevant to the understanding of the electronic structure of the cuprates in the normal state, to other oxide superconductors and to fulleride superconductors.

A broad introduction to high Tc superconductors, their parent compounds and related novel materials, covering both fundamental questions of modern solid state physics (such as correlation effects, fluctuations, unconventional symmetry of superconducting order parameter) and applied problems related to short coherence length, grain boundaries and thin films. The information that can be derived from electron spectroscopy and optical measurements is illustrated and explained in detail. Descriptions widely employ the clear, relatively simple, phenomenological Ginzburg-Landau model of complex phenomena, such as vortex physics, vortex charge determination, plasmons in superconductors, Cooper pair mass, and wetting of surfaces. The first comprehensive reviews of several novel classes of materials are presented, including borocarbides and chain cuprates.

This volume deals with an important aspect of the physics of high-temperature superconductors. In recent years a wealth of experimental and theoretical work has accumulated on the subject of anharmonicity in connection to either superconductivity or lattice properties of superconducting oxides. The papers, by leading experts, are the proceedings of the first workshop dedicated to dealing with these issues.

Introduction to Solid-State Theory is a textbook for graduate students of physics and materials science. It also provides the theoretical background needed by physicists doing research in pure solid-state physics and its applications to electrical engineering. The fundamentals of solid-state theory are based on a description by delocalized and localized states and - within the concept of delocalized states - by elementary excitations. The development of solid-state theory within the last ten years has shown that by a systematic introduction of these concepts, large parts of the theory can be described in a unified way. This form of description gives a "pictorial" formulation of many elementary processes in solids, which facilitates their understanding.

This book reports new results in condensed matter physics for which topological methods and ideas are important. It considers, on the one hand, recently discovered systems such as carbon nanocrystals and, on the other hand, new topological methods used to describe more traditional systems such as the Fermi surfaces of normal metals, liquid crystals and quasicrystals. The authors of the book are renowned specialists in their fields and present the results of ongoing research, some of it obtained only very recently and not yet published in monograph form.

The experimental discovery of the fractional quantum Hall effect (FQHE) at the end of 1981 by Tsui, Stormer and Gossard was absolutely unexpected since, at this time, no theoretical work existed that could predict new struc tures in the magnetotransport coefficients under conditions representing the extreme quantum limit. It is more than thirty years since investigations of bulk semiconductors in very strong magnetic fields were begun. Under these conditions, only the lowest Landau level is occupied and the theory predicted a monotonic variation of the resistivity with increasing magnetic field, depending sensitively on the scattering mechanism. However, the ex perimental data could not be analyzed accurately since magnetic freeze-out effects and the transitions from a degenerate to a nondegenerate system complicated the interpretation of the data. For a two-dimensional electron the positive background charge is well separated from the two gas, where dimensional system, magnetic freeze-out effects are barely visible and an analysis of the data in the extreme quantum limit seems to be easier. First measurements in this magnetic field region on silicon field-effect transistors were not successful because the disorder in these devices was so large that all electrons in the lowest Landau level were localized. Consequently, models of a spin glass and finally of a Wigner solid were developed and much effort was put into developing the technology for improving the quality of semi conductor materials and devices, especially in the field of two-dimensional electron systems.

The focus of the workshop is the role of crystal lattices, i.e. atomic structure, phonons, lattice distortions, in the mechanism of high temperature superconductivity in oxides. In spite of the intense research effort during the last five years the mechanism of high temperature superconductivity still remains unknown. While earlier theories forcused primarily on the role of magnetic interaction, recent experimental results strongly suggest that anharmonic local atomic displacements, in particular those induced by charge carriers, are critically involved in creating high temperature superconductivity. In this workshop, experimentalists and theoreticians address this issue with the hope of stimulating real progress in this area.

Six papers by physicists from the Japan, India, Brazil and the US address some of the broad frontal issues of superconductivity, which include the mechanisms of high-temperature superconductivity, extra-high-temperature phenomena, the normal state pseudogap, the observations of the isotope effect in a host of different superconducting systems and their explanations, and the unusual features of strongly correlated electron systems like heavy fermions. Two extended papers explore the importance of positron annihilation and using electron spin resonance techniques to study superconducting materials. The treatments should be accessible to working scientists and engineers and to graduate students of physics, chemistry, materials science, solid-state electronics, and other disciplines.

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.