Electron–phonon interaction of quantum-well states on Ag nanofilms studied by temperature-dependent photoemission spectroscopy

Abstract

We have carried out a temperature-dependent angle-resolved photoemission study for Ag(111) nanofilms grown on Cu(111) substrates. The valence band photoemission spectra of Ag nanofilms exhibit the features associated with the quantum-well (QW) states. It is found that the linewidth of the QW state broadens systematically with increasing temperature from 40 to 350 K and it depends linearly on the temperature. The observed temperature dependence is explained as the phonon contribution to the inverse hole lifetime. It is indicated that these results allow the discussion of the electron–phonon interaction through the electron–phonon mass enhancement parameter λ , which enters the linewidth as 2π λk B T. The experimental electron–phonon mass enhancement parameters for the QW states have been compared to that for surface state on the Ag(111) surface and that reported as an average over the bulk Fermi surface.