Introduction

Abstract

The advent of quantum mechanics in the early twentieth century has fundamentally improved our understanding of the physics of matter in general and of the solid state in particular. Consisting of a very large number of atoms, solids exhibit a rich variety of material properties, whose understanding represents a challenge to the curious scientist. These properties are at the same time a rich source for technical applications. Consequently, in the course of the last century our increasing knowledge about the relationship between the chemical composition and the structure of solids on one side and their particular properties – according to which we identify metals, semiconductors, superconductors, and magnetic materials – on the other side, has led to the invention of an enormous variety of solid state devices. Whole industries have been created based on products that make use of solid state properties. Transistors, sensors, solid state lasers, light-emitting diodes (LED), superconducting quantum interference devices (SQUID), dynamic and magnetic random access memories (DRAM and MRAM) have become essential parts of electronic appliances such as computers, mobile phones, compact disc (CD) and digital video disc (DVD) players, which have revolutionized our daily life and continue to do so. The impressive development in the technology of data storage and handling, symbolized by Moore's law, demonstrates an unprecedented technological progress, which, though driven by the market, would be unthinkable without the ingenious investigations of generations of physicists.