Electronic-structure dependence of the electron-phonon interaction in Ag.

The linewidths of sp- and d-band derived electronic quantum-well states in thin films of Ag on Fe(100) are measured as a function of temperature to yield the electron-phonon coupling parameters. The results vary by a factor of up to 35 among the different states. The origin of these huge differences is traced to the decay path selection for the various initial states of the holes created by the photoemission process. The electron-phonon coupling parameter for the top d-band quantum-well state, 0.015+/-0.006, is the smallest ever reported.

Large electron-phonon coupling at an interface.

The strength of electron-phonon coupling in atomically uniform films of Ag on Fe is determined by angle-resolved photoemission from quantum well states in these films over a wide temperature range. As the film thickness is reduced, contributions from the surface and interface should become more important, and, experimentally, a large enhancement with superimposed quantum oscillations is observed. An analysis of the quantum oscillations indicates that this large enhancement is an interface effect.

Quantum electronic stability of atomically uniform films.

We have studied the structural stability of thin silver films with thicknesses of N = 1 to 15 monolayers, deposited on an Fe(100) substrate. Photoemission spectroscopy results show that films of N = 1, 2, and 5 monolayer thicknesses are structurally stable for temperatures above 800 kelvin, whereas films of other thicknesses are unstable and bifurcate into a film with N +/- 1 monolayer thicknesses at temperatures around 400 kelvin. The results are in agreement with theoretical predictions that consider the electronic energy of the quantum well associated with a particular film thickness as a significant contribution to the film stability.