What Angle-Resolved Photoemission Experiments Tell about the Microscopic Theory for High-Temperature Superconductors

The discovery of the copper oxide superconducting materials in 1987 and the intense investigations which followed have raised some fundamental questions in condensed matter physics. These superconductors are characterized by two unexpected features. One is, of course, their unprecedented high transition temperatures (T sub c). In addition it is clear that their normal-state properties are not those of ordinary metals; they are not consistent with the traditional Fermi-liquid quasiparticle picture which is a cornerstone of our understanding of the metallic state.