The characteristics of electrical contacts have long attracted the attention of researchers since these contacts are used in every electrical and electronic device. Earlier studies generally considered electrical contacts of large dimensions, having regions of current concentration with diameters substantially larger than the characteristic dimensions of the material: the interatomic distance, the mean free path for electrons, the coherence length in the superconducting state, etc. [110]. The development of microelectronics presented to scientists and engineers the task of studying the characteristics of electrical contacts with ultra-small dimensions. Characteristics of point contacts such as mechanical stability under continuous current loads, the magnitudes of electrical fluctuations, inherent sensitivity in radio devices and nonlinear characteristics in connection with electromagnetic radiation can not be understood and altered in the required way without knowledge of the physical processes occurring in contacts. Until recently it was thought that the electrical conductivity of contacts with direct conductance (without tunneling or semiconducting barriers) obeyed Ohm's law. Nonlinearities of the current-voltage characteristics were explained by joule heating of the metal in the region of the contact. However, studies of the current-voltage characteristics of metallic point contacts at low (liquid helium) temperatures [142] showed that heating effects were negligible in many cases and the nonlinear characteristics under these conditions were observed to take the form of the energy dependent probability of inelastic electron scattering, induced by various mechanisms.

This monograph is a radical departure from the conventional quantum mechanical approach to electron-phonon interactions. It translates the customary quantum mechanical analysis of the electron-phonon interactions carried out in Fourier space into a predominantly classical analysis carried out in real space. Various electron-phonon interactions such as the polar and nonpolar optical phonons, acoustic phonons that interact via deformation potential and via the piezoelectric effect and phonons in metals, are treated in this monograph by a single, relatively simple ?classical? model. This model is shown to apply to electron interactions with the deep lying X-ray levels of atoms, with plasmons and with Cerenkov radiation. The unifying concept that applies to all of these phenomena is a new definition of a coupling constant. The essentially classical interaction of an electron with its surrounding is clearly brought out to be the cause of spontaneous emission of phonons. The same concept also applies to the case of spontaneous emission of photons. While the bulk of this monograph deals with quanta of phonons and quanta of photons, a discussion of the acousto electric effect which is a purely classical phenomenon is presented. The newly defined coupling constant turns out to be valid too for this discussion. This universality of the coupling constant goes far beyond. It is equally applicable to amorphous materials. This significant application gives an analytic formulation of mobility in amorphous materials.

The study of cooperative phenomena is one of the dominant features of contem porary physics. Outside physics it has grown to a huge field of interdisciplinary investigation, involving all the natural sciences from physics via biology to socio logy. Yet, during the first few decades following the advent of quantum theory, the pursuit of the single particle or the single atom, as the case may be, has been so fascinating that only a small number of physicists have stressed the importance of collective behaviour. One outstanding personality among these few is Professor HERBERT FROHLICH. He has made an enormous contribution to the modern concept of cooperativity and has stimulated a whole generation of physicists. Therefore, it seemed to the editors very appropriate to dedicate a volume on "cooperative phenomena" to him on the occasion of his official retirement from his university duties. Nevertheless, in the course of carrying out this project, the editors have been somewhat amazed to find that they have covered the essentials of contemporary physics and its im pact on other scientific disciplines. It thus becomes clear how much HERBERT FROHLICH has inspired research workers and has acted as a stimulating discussion partner for others. FROHLICH is one of those exceptional scientists who have wor ked in quite different fields and given them an enormous impetus. Unfortunately, the number of scientists of such distinctive personality has been decreasing in our century.

This is a classic text of its time in condensed matter physics.

A distinctive introduction to the principles governing polaron science for experimental and theoretical graduate students and researchers.

This is a thoroughly revised version of the original book published in 1986. About half of the contents of the previous version remain essentially unchanged, and one quarter has been rewritten and updated. The rest consists of completely new and extended material. Recent research has focussed on new materials made through "molecular engineering", and computational materials science through ab initio electron structure calculations. Another trend is the ever growing interdisciplinary aspect of both basic and applied materials science. There is an obvious need for reviews that link well established results to the modern approaches. One purpose of this book is to provide such an overview in a specific field of materials science, namely thermophysical phenomena that are intimately connected with the lattice vibrations of solids. This includes, e.g., elastic properties and electrical and thermal transport. Furthermore, this book attempts to present the results in such a form that the reader can clearly see their domain of applicability, for instance if and how they depend on crystal structure, defects, applied pressure, crystal anisotropy etc. The level and presentation is such that the results can be immediately used in research. Graduate students in condensed matter physics, metallurgy, inorganic chemistry or geophysical materials will benefit from this book as will theoretical physicists and scientists in industrial research laboratories.

Applying a unified quantum approach, contributors offer fresh insights into the theoretical developments in the excitation energy transfer processes in condensed matter. This comprehensive volume examines Frenkel and Wannier excitonic processes; rates of excitonic processes; theory of laser sputter and polymer ablation; and polarons, excitonic polarons and self-trapping.