Theoretical and experimental work on solids with low-dimensi℗Ư onal cooperative phenomena has been rather explosively expanded in the last few years, and it seems to be quite fashionable to con℗Ư tribute to this field, especially to the problem of one-dimensional metals. On the whole, one could divide the huge amount of recent investigations into two parts although there is much overlap bet℗Ư ween these regimes, namely investigations on magnetic exchange interactions constrained to mainly one or two dimensions and, secondly, work done on Id metallic solids or linear chain compounds with Id delocalized electrons. There is, of course, overlap from one extreme case to the other with these solids and in some rare cases both phenomena are studied on one and the same crystal. In fact, however, most of the scientific groups in this area could be associated roughly with one of these categories and, in addition, a separation between theoreticians and experimentalists in each of these groups leads to a further splitting of interests although many theories about these solids have been tested by experimenta℗Ư lists. Nevertheless, more cooperation and understanding between scientists working on low-dimensional cooperative phenomena should appreciably stimulate further development. With a better inderdis℗Ư ciplinary understanding, new ideas could possibly help chemists in synthesizing tailor-cut solids. This would in return give experi℗Ư mentalists new phenomena to examine and finally would stimulate new theoretical work.

Proceedings of the NATO Advanced Study Institute, Tomar, Portugal, August 26-September 7, 1979

Fermi Surfaces of Low-Dimensional Organic Metals and Superconductors is an introduction to quasi-one- and quasi-two-dimensional organic metals and a review of the current knowledge on the electronic structure of these materials. The principal structural, electronic, and superconducting properties are described and illustrated with many examples. The book introduces the basic theoretical concepts necessary for the understanding of the experimental techniques and reviews in detail recent results in the investigation of the Fermi surface topology. The book is intended both as an introduction and as a reference book for active researchers.

tailor-made molecules and indicated what kind of compounds could be prepared in the near future. In several evening and weekend sessions some participants presented summaries of their recent work and these and other new results were discussed. A draft of these discussions could not be added in printed form because of the 1 imitations set by the total page number of this volume, but to give at least an idea of the problems touched upon during these sessions, a 1 ist of the main contributors together with the title of the conribution discussed is given as an appendix. The reader might contact these authors directly if interested in special recent results. I hope that the participants have profited from the meeting and, furthermore, that at least some of the readers of the following papers are stimulated to high-dimensional cooperative efforts on low-dimensional conductive sol ids. Primarily I have to thank NATO who made this project possible through generous financial support. Especially I would 1 ike to men tion gratefully the excellent cooperation with Dr. T. Kester of the NATO Scientific Affairs Division, whose personal efforts helped in the preparation and organization of the meeting. The Advanced Study Institute could not have taken place without the efforts of Mrs.

Although the problem of a metal in one dimension has long been known to solid-state physicists, it was not until the synthesis of real one-dimensional or quasi-one-dimensional systems that this subject began to attract considerable attention. This has been due in part to the search for high temperature superconductivity and the possibility of reaching this goal with quasi-one-dimensional substances. A period of intense activity began in 1973 with the report of a measurement of an apparently divergent conduc tivity peak in TfF-TCNQ. Since then a great deal has been learned about quasi-one-dimensional conductors. The emphasis now has shifted from trying to find materials of very high conductivity to the many interesting problems of physics and chemistry involved. But many questions remain open and are still under active investigation. This book gives a review of the experimental as well as theoretical progress made in this field over the last years. All the chapters have been written by scientists who have established themselves as experts in theoreti cal and experimental solid-state physics. The book is intended to be of use both to students and researchers entering the field as well as to more advanced physicists. The wealth of ideas and information it contains ought to be useful to anyone interested in quasi-one-dimensional systems, organic solids, or the search for novel conduction and superconduction mechanisms. The editors are very grateful to the authors for their collaboration in this book.

?Density Waves in Solids is written for graduate students and scientists interested in solid-state sciences. It discusses the theoretical and experimental state of affairs of two novel types of broken symmetry ground states of metals, charge, and spin density waves. These states arise as the consequence of electron-phonon and electron-electron interactions in low-dimensional metals.Some fundamental aspects of the one-dimensional electron gas, and of the materials with anisotropic properties, are discussed first. This is followed by the mean field theory of the phases transitions?discussed using second quantized formalism?together with the various experimental observations on the transition and on the ground states. Fluctuation effects and the collective excitations are reviewed next, using the Ginzburg-Landau formalism, followed by the review of the interaction of these states with the underlying lattice and with impurities. The final chapters are devoted to the response of the ground states to external perturbations.

The area of high field transport in semiconductors has been of interest since the early studies of dielectric breakdown in various materials. It really emerged as a sub-discipline of semiconductor physics in the early 1960's, following the discovery of substantial deviations from Ohm's law at high electric fields. Since that time, it has become a major area of importance in solid state electronics as semiconductor devices have operated at higher frequencies and higher powers. It has become apparent since the Modena Conference on Hot Electrons in 1973, that the area of hot electrons has ex tended weIl beyond the concept of semi-classical electrons (or holes) in homogeneous semiconductor materials. This was exemplified by the broad range of papers presented at the International Conference on Hot Electrons in Semiconductors, held in Denton, Texas, in 1977. Hot electron physics has progressed from a limited phenomeno logical science to a full-fledged experimental and precision theo retical science. The conceptual base and subsequent applications have been widened and underpinned by the development of ab initio nonlinear quantum transport theory which complements and identifies the limitations of the traditional semi-classical Boltzmann-Bloch picture. Such diverse areas as large polarons, pico-second laser excitation, quantum magneto-transport, sub-three dimensional systems, and of course device dynamics all have been shown to be strongly interactive with more classical hot electron pictures.

This volume deals with physical properties of electrically one-dimensional conductors. It includes both a description of basic concepts and a review of recent progress in research. One-dimensional conductors are those materials in which an electric current flows easily in one specific crystal direction while the resistivity is very high in transverse directions. It was about 1973 when much attention began to be focussed on them and investigations started in earnest. The research was stimulated by the successful growth of crystals of the organic conductor TTF-TCNQ and of the inorganic conductor KCP. New concepts, characteristic of one dimension, were established in the in vestigations of their properties. Many new one-dimensional conductors were also found and synthesized. This field of research is attractive because of the discovery of new ma terials, phenomena and concepts which have only recently found a place in the framework of traditional solid-state physics and materials science. The relation of this topic to the wider field of solid-state sciences is therefore still uncertain. This situation is clearly reflected in the wide distribution of the fields of specialization of researchers. Due to this, and also to the rapid progress of research, no introductory book has been available which covers most of the important fields of research on one-dimensional conductors.

In 1966, E.H. Lieb and D.C. r1attis published a book on "Mathematical Physics in One Dimension" [Academic Press, New York and London] which is much more than just a collection of reprints and which in fact marked the beginnings of the rapidly growing interest in one-dimensional problems and materials in the 1970's. In their Foreword, Lieb and r~attis made the observation that " ... there now exists a vast literature on this subject, albeit one which is not indexed under the topic "one dimension" in standard indexing journals and which is therefore hard to research ... ". Today, the situation is even worse, and we hope that these Proceedings will be a valuable guide to some of the main current areas of one-dimensional physics. From a theoretical point of view, one-dimensional problems have always been very attractive. Many non-trivial models are soluble in one dimension, while they are only approximately understood in three dimensions. Therefore, the corresponding exact solutions serve as a useful test of approximate ma thematical methods, and certain features of the one-dimensional solution re main relevant in higher dimensions. On the other hand, many important phe nomena are strongly enhanced, and many concepts show up especially clearly in one-dimensional or quasi -one-dimensional systems. Among them are the ef fects of fluctuations, of randomness, and of nonlinearity; a number of in teresting consequences are specific to one dimension.