Large Facilities for Condensed-Matter Science

Abstract

The structural perfection and the optical beauty of natural crystals have always been a source of fascination. The attempt to provide a scientific understanding of crystal structure—to understand the natural laws that underlie the aesthetic appeal—marked the beginning of condensed-matter physics. This intellectual revolution began in 1912, when Walter Friedrich, Paul Knipping and Max von Laue presented an elementary theory of xray diffraction by crystals and reported the first experimental results. Remarkably, this monumental work not only heralded the modern era of condensedmatter physics, it demonstrated conclusively the wave nature of x rays—one cornerstone in the modern development of physics. The discovery of electron and neutron diffraction—in 1926 and 1936, respectively—greatly increased the range of phenomena that could be studied in condensed matter. Today the quest for useful new probes continues; muons and positrons, for example, are being investigated. However, it is overwhelmingly clear that electrons, neutrons and photons are still the most important probes in their collective contributions to our field and their potential for future discovery. The profound impact these probes have had on the microscopic understanding of materials becomes clear when one asks questions such as: What would we know about the geometric and electronic structure of solids without photon scattering and spectroscopy? What would we know about magnetism, phase transitions and excitations in solids without neutron scattering?