Photoemission studies of high-temperature superconductors

A review of photoemission measurements on high-temperature superconductors is presented. Earlier photoemission results and interpretations are critically examined, providing the reader with an overview of the present status of the field. Special emphasis is paid to recent progress, in particular the revelation of the superconducting gap, and angle-resolved photoemission studies of high-quality single crystals of the Bi2Sr2CaC2O8 material. Comparison with predictions of band calculations and impurity model calculations as well as the electronic structure of some transition-metal oxides is made. Finally, comments on the present status of photoemission studies of the high-temperature superconductors and future implications are given.