High-resolution temperature-dependent valence-band photoemission spectroscopy of gold:mNature of electron-phonon coupling

Using high-resolution temperature-dependent (20--400 K) valence-band photoemission spectroscopy, we study the nature of electron-phonon coupling in polycrystalline gold. The valence band shows systematic broadening for increasing temperatures which is well-reproduced by a Gaussian broadening of the 20 K spectrum. It depends linearly on temperature and is found to be excessive ({~}9 kB T). The results suggest the existence of anharmonic lattice vibrations and a quadratic electron-phonon coupling, similar to the case of aluminum 2p core levels.