Temperature Dependent Complex Band Structure and Electron-Phonon Coupling in Ag

The band dispersion and lifetime width for the sp valence electrons in Ag are determined with unprecedented accuracy as a function of temperature. The resulting Fermi wave vector challenges the venerable de Haas--van Alphen value, and shows the latter to be off by 1%. The electron-phonon mass enhancement parameter is deduced for the first time for a bulk state, and it is significantly larger than theoretical estimates. These measurements are made by photoemission from quantum well states in atomically uniform films of Ag.