Electronic Structure and Dynamics of Quantum-Well States in thin Yb-Metal Films

By low-temperature scanning tunneling spectroscopy, we have studied quantum-well states above the Fermi energy in thin Yb(111)- metal films deposited on a W(110) single crystal. These states are laterally highly localized and give rise to sharp peaks in the tunneling spectra. Due to the high lateral resolution of STS, the quantum-well states and their film-thickness dependence can be observed on rather rough films with variations of the local thickness over a range of several monolayers. A quantitative analysis of the spectra yields the bulk-band dispersion in $\Gamma - \mbox{L}$ direction as well as quasi-particle lifetimes. The quadratic energy dependence of the lifetimes is in quantitative agreement with Fermi-liquid theory. cond-mat/0411580.