Preface to the Study Edition
The precursor of this book was first published in German in three paperbacks in the series "Heidelberger Taschenbücher". Its great success led to the improved English textbook, which - after a revised second printing - is now out of print.
I am grateful to Springer, for publishing a Study Edition instead of a new edition of the hardcover textbook. By its reduced price it will be available to a wider circle of students and scientists interested in the basics of solid-state theory.
Marburg, January 1995
From the Preface to the First Edition
This book is intended for graduate students of physics, materials science, and electrical engineering as a textbook in solid-state theory. In addition, it should provide the theoretical background needed by research physicists in solid-state physics and in the solid-state areas of electrical engineering.
The content of this book and the level of presentation are determined by the needs of its intended audience. The field of solid-state physics has grown so large that some selection of topics has to be made. In a book on solidstate physics it is still possible to survey the full range of solid-state phenomena and to connect them by a qualitative presentation of theoretical concepts. However, in a text introducing solid-state theory, a presentation of all theoretical concepts and methods seemed inappropriate. For this reason I have tried to develop the fundamentals of solid-state theory starting from a single unifying point of view-the description by delocalized (extended) and localized states and by elementary excitations. The development of solid-state theory within the last ten years has shown that by a systematic introduction of those concepts large parts of the theory can be described in a unified way. At the same time this form of description gives a "pictorial" formulation of many elementary processes in solids which facilitates their understanding.
Admittedly the attempt to present solid-state physics under one unifying aspect has its shortcomings. Not all parts of solid-state theory fit naturally into this frame. But the limitations imposed by such organization of the book seemed to me justified for several reasons. First, because there are only a few topics which do not fit into this type of description, the range covered is representative of the predominant part of solid-state theory. Secondly, the manner of description chosen seems especially suited for those areas of solidstate physics which are dominant in the application to solid-state electronics. Finally, since so many valuable textbooks and monographs on solid-state theory are available, a new book should intend to complement them rather than to compete.
I have tried to offer a general framework of solid-state theory which the reader can fill in from the more specialized material provided by monographs, review articles, and original papers. In this book, some fields are described in detail and some fields are treated more briefly. Topics which have been covered by comprehensive monographs are in some cases presented here only from the viewpoint of elementary excitations. Thus, spin-waves are emphasized in the chapter on magnetism. The electron-electron interaction by exchange of virtual phonons is the central topic in the chapter on superconductivity, whereas other important aspects of this field are only mentioned briefly. In every case, however, I have tried to inform the reader as completely as possible about additional available literature.
It was not my intention to write a book on solid-state theory for the prospective solid-state theorist. I therefore intentionally refrained from using the abstract methods of quantum field theory, important as they are in manybody problems. The general use of these methods seems to me inappropriate for the broad audience to whom this book is directed. On the other hand, some prior knowledge of elementary quantum mechanics as well as of the most important solid-state phenomena is required and assumed. Because of the close connection of all fields of solid-state physics, from the basic theoretical concepts to the technical applications, I have made use of Si-units (Système International) throughout, in contrast to most other textbooks in this field. To each chapter some problems are added. Most of them are not intended to train the reader in theoretical methods but to direct his attention to applications and additional questions which arise from the respective sections. Many of the problems have already been discussed in other monographs or review articles. I have indicated such sources in the Bibliography.
Marburg, April 1978