Two-Dimensional Systems: Physics and New Devices


Book Description

In the series of International Winter Schools on New Developments in Solid State Physics, the fourth one was devoted to the subject: "Two Dimensional Systems: Physics and Devices". For the second time the pro ceedings of one of these Winter Schools appear as a volume in the Springer Series in Solid-State Sciences (the earlier proceedings were published as Vol. 53). The school was held in the castle of MauterndorfjSalzburg (Austria) February 24-28, 1986. These proceedings contain contributions ba:sed on the thirty invited lectures. The school was attended by 179 registered participants (40% students), who came from western European countries, the United States of America, Japan, the People's Republic of China and Poland. As far as the subjects are conterned, several papers deal with the growth and characterization of heterostructures. Dynamical RHEED tech niques are described as a tool for in situ studies of MBE growth mech anisms. Various growth techniques, including MBE, MOMBE, MOCVD and modifications of these, are discussed. The limiting fa.ctors for the carrier mobilities and the inftuence of the spacer thickness in single het erostructures of GaAs/GaAIAs seem to be understood and are no longer a matter of controversy. In addition, the growth of two fascinating systems, Si/SiGe and Hg _ Cd Te/CdTe, is discussed in detail




Two-Dimensional Electron Systems


Book Description

Recent studies on two-dimensional systems have led to new insights into the fascinating interplay between physical properties and dimensionality. Many of these ideas have emerged from work on electrons bound to the surface of a weakly polarizable substrate such as liquid helium or solid hydrogen. The research on this subject continues to be at the forefront of modern condensed matter physics because of its fundamental simplicity as well as its connection to technologically useful devices. This book is the first comprehensive overview of experimental and theoretical research in this exciting field. It is intended to provide a coherent introduction for graduate students and non-experts, while at the same time serving as a reference source for active researchers in the field. The chapters are written by individuals who made significant contributions and cover a variety of specialized topics. These include the origin of the surface states, tunneling and magneto-tunneling out of these states, the phase diagram, collective excitations, transport and magneto-transport.




The Physics of Low-dimensional Semiconductors


Book Description

The composition of modern semiconductor heterostructures can be controlled precisely on the atomic scale to create low-dimensional systems. These systems have revolutionised semiconductor physics, and their impact on technology, particularly for semiconductor lasers and ultrafast transistors, is widespread and burgeoning. This book provides an introduction to the general principles that underlie low-dimensional semiconductors. As far as possible, simple physical explanations are used, with reference to examples from actual devices. The author shows how, beginning with fundamental results from quantum mechanics and solid-state physics, a formalism can be developed that describes the properties of low-dimensional semiconductor systems. Among numerous examples, two key systems are studied in detail: the two-dimensional electron gas, employed in field-effect transistors, and the quantum well, whose optical properties find application in lasers and other opto-electronic devices. The book includes many exercises and will be invaluable to undergraduate and first-year graduate physics or electrical engineering students taking courses in low-dimensional systems or heterostructure device physics.




Magnetism and the Electronic Structure of Crystals


Book Description

The quantum theory of magnetism is a well-developed part of contemporary solid-state physics. The basic concepts of this theory can be used to describe such important effects as ferromagnetic ordering oflocalized magnetic moments in crystals and ferromagnetism of metals produced by essentially delocalized electrons, as well as various types of mutual orientation of atomic magnetic moments in solids possessing different crystal lattices and compositions. In recent years,the spin-fluctuational approach has been developed, which can overcome some contradictions between "localized" and "itinerant" models in the quantum mechanics of magnetic crystals. These are only some of the principal achievements of quantum magnetic theory. Almost all of the known magnetic properties of solids can be qualitat ively explained on the basis of its concepts. Further developments should open up the possibility of reliable quantitative description of magnetic properties of solids. Unfortunately, such calculations based on model concepts appear to be very complicated and, quite often, not definite enough. The rather small number of parameters of qualitative models are usually not able to take into account the very different types of magnetic interactions that appear in crystals. Further development of magnetic theory requires quantitative information on electronic wave function in the crystal considered. This can be proved by electronic band structure and cluster calculations. In many cases the latter can be a starting point for quantitative calculations of parameters used in magnetic theory.




Electronic Conduction in Oxides


Book Description

This book is a revised and up-dated translation of Denki DendOsei Sankabutsu (Electronic Conduction in Oxides) published by Shokabo in Tokyo in 1983 as the second volume of the Material Science Series, which was edited for postgraduate students by T. Suzuki, S. Chikazumi, and S. Nakajima. Since the publication of the first edition, we have witnessed the historic discovery of high-Tc superconductors by J. G. Bednorz and K. A. Müller. Tbe Shokabo edition has thus been thoroughly revised to accommodate the recent developments, and K. Nasu joined as the fourth author. The constitution of the book is as follows: After a short introductory chapter, Chap. 2 is devoted 10 a brief review of transport phenomena and electronic states in oxides. It was written by Tsuda. In Chap. 3, the electron-phonon and electron electron interaction are treated theoretically by Nasu and Yanase. Nasu discusses the present status of theoretical studies of the electron-phonon interaction in solids and Yanase explains the electron correlation. Chapter 4 treats the physics ofvarious representative oxides in detail. Sections 4. 1-5 and 4. 10 were written by Tsuda and Sects. 4. 6-9 by Siratori. This chapter is intended not as an exhaustive review of the properties of each oxide, but rather as an illustration of the concepts which have developed out of the research into transport phenomena in conductive oxides. Many of these concepts are due 10 N. F. Mott. At the end of Chap.




Beyond the Crystalline State


Book Description

Condensed matter exhibits a rich variety of phases. Of these, the crystalline state has, until recently, received most attention. This is not surprising, given the geometric regularity of crystals. At the other extreme one has amorphous materials. In between there are the various types of liquid crystals, the recently discovered quasicrystals, and so on. While the absence of the high degree of regularity that characterizes the crystalline phase is certainly a problem, these noncrystalline states have nevertheless been receiving some attention over the years. However, it is only during the last few years that something like a uni fied view of all these phases has begun to emerge, through an application of various sophisticated concepts. Geometry and symmetry (and unusual realiza tions of the latter) provide a unifying thread in this new and emerging perspec tive. This book is an attempt to capture the flavour of some of these recent de velopments. The approach is substantially descriptive, being intended to be accessible not only to experimental physicists, but also to chemists, materials scientists, metallurgists and ceramicists, whose work borders on physics. The prerequisites for a study of this book are a familiarity with basic solid-state physics and, in places, the elements of group theory and statistical mechanics. A few special topics are included at the end to aid those who wish to pur sure further the subject matter treated here.




Theory of Nonlinear Lattices


Book Description

Soliton theory, the theory of nonlinear waves in lattices composed of particles interacting by nonlinear forces, is treated rigorously in this book. The presentation is coherent and self-contained, starting with pioneering work and extending to the most recent advances in the field. Special attention is focused on exact methods of solution of nonlinear problems and on the exact mathematical treatment of nonlinear lattice vibrations. This new edition updates the material to take account of important new advances.




Electronic Structure and Optical Properties of Semiconductors


Book Description

We began planning and writing this book in the late 1970s at the suggestion of Manuel Cardona and Helmut Lotsch. We also received considerable en couragement and stimulation from colleagues. Some said there was a need for instructional material in this area while others emphasized the utility of a research text. We tried to strike a compromise. The figures, tables, and references are included to enable researchers to obtain quickly essential information in this area of semiconductor research. For instructors and stu dents, we attempt to cover some basic ideas about electronic structure and semiconductor physics with applications to real, rather than model, solids. We wish to thank our colleagues and collaborators whose research re sults and ideas are presented here. Special thanks are due to Jim Phillips who influenced us both during our formative years and afterwards. We are grateful to Sari Yamagishi for her patience and skill with the typing and production of the manuscript. Finally, we acknowledge the great patience of Helmut Lotsch and Manuel Cardona. Berkeley, CA M.L. Cohen Minneapolis, MN, J.R. Chelikowsky March 1988 VII Contents 1. Introduction............................................... 1 2. Theoretical Concepts and Methods ..................... 4 2.1 The One-Electron Model and Band Structure............ 7 2.2 Properties of En(k) ...................................... 11 3. Pseudopotentials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 . . . . . . . . . . . . 3.1 The Empirical Pseudopotential Method.................. 20 3.2 Self-Consistent and Ab Initio Pseudopotentials ........... 25 4. Response Functions and Density of States .............. 30 4.1 Charge Density and Bonding ................... . . . . . . . . . 38 .




Quantum Wells


Book Description

This invaluable book is devoted to the physics, technology and device applications of semiconductor structures with ultrathin layers where the electronic properties are governed by the quantum-mechanical laws. Such structures called quantum wells or structures with the two-dimensional electron gas, have become one of the most actively investigated objects in modern solid state physics. Electronic properties of quantum wells differ dramatically from those of bulk semiconductors, which allows one to observe new types of physical phenomena, such as the quantum Hall effect and many other so-far-unknown kinetic and optical effects. This, in turn, offers wide opportunities for creating semiconductor devices based on new principles, and it has give birth to the new branch of electronics called nanoelectronics.




Organic Superconductors


Book Description

The initial impetus for the search for an organic superconductor was the proposal of the existence of a polymer superconductor with a high critical temperature (Tc). This spurred on activities having the aim of synthesizing and characterizing organic conductors, which had already been going on for two decades. These efforts have resulted in the thriving field of low dimensional conductors and superconductors. This monograph is intended to be an introduction to and review of the study of organic conductors and superconductors. The investigations are to warrant a treatise of some length. At the same time sufficiently rich they have produced a few active subfields, each containing exciting topics. This situation seems to necessitate a monograph describing the current status of the field for both researchers and newcomers to the field. Such a need may also be felt by scientists engaged in the study of the high-Tc oxide superconductors for comparison of the two kinds of new supercon ductors, which share some important aspects, for example, the low-dimen sionality and the competition or coexistence of superconductivity and magnetism. However, available experimental and theoretical results are sometimes conflicting and have not yet been arranged into a coherent standard picture of the whole field. Further developments are continually being reported and therefore it is still premature to write a textbook about some of the topics. However, we have tried to include discussions of recent topics in this volume.