We present a comprehensive theoretical investigation of the electron-phonon contribution to the lifetime broadening of the surface states on Cu(111) and Ag(111), in comparison with high-resolution photoemission results. The calculations, including electron and phonon states of the bulk and the surface, resolve the relative importance of the Rayleigh mode, being dominant for the lifetime at small hole binding energies. Including the electron-electron interaction, the theoretical results are in excellent agreement with the measured binding energy and temperature dependent lifetime broadening. Understanding the temporal evolution of quasi particles (electron and holes) on metal surfaces is of paramount importance to describe many important phenomena such as the dynamics of charge and energy transfer, quantum interference, localization and many others. This temporal evolution is characterized by a finite lifetime, τ , which refers to the time the quasi particle retains its identity. While the lifetime of an excited electron or hole is determined by many-body interactions, namely electron-electron (e-e) and electron-phonon (e-p) scattering processes, the peak width in an experiment might also be influenced by electron-defect scattering on crystal or surface imperfections [1]. However, it was demonstrated in recent STM [2] and photoemission experiments [3] that these defect contributions can be minimized, making it possible to analyze the pure lifetime broadening due to the formation of a hole in the sp surface state band in the L-gap of the (111)-surface of noble metals.These Shockley-type surface states form a twodimensional (2D) electron gas and the e-e contribution to the hole lifetime has been rationalized in terms of a dominant contribution from intraband transitions within the 2D surface state band, screened by the underlying 3D bulk electron system, and in terms of interband transitions (bulk states → surface state) [2]. On the other hand an appropriate calculation of the e-p contribution to the lifetime broadening of surface states is still lacking. The present work is an attempt in this direction.The strength of the e-p coupling is described by the electron mass enhancement parameter λ, which is, in general, energy and momentum dependent. Many properties of metals [4], such as resistivity, specific heat and superconductivity, reflect the e-p coupling and can be expressed in terms of the Fermi surface-averaged λ-value. It also reflects the high temperature behavior of the broadening Γ ep = 2πλk B T , and the e-p contribution to the renormalization of the mass m * = m(1 + λ). The anisotropy of λ is well known [5] and is revealed in e.g. cyclotron resonance measurements [6].Typically, the phonon contribution to the decay of surface states is estimated using the Debye phonon model. Within this model the Eliashberg spectral function of the e-p interaction is proportional to the quadratic density of phonon states α 2 F (ω) = λ(ω/ω D ) 2 , where ω D is the Debye energy, λ is usually obtained from measurements or th...

Using a consistent quantum-mechanical treatment for the electromagnetic radiation, we theoretically investigate the magnetic spin-flip scatterings of a neutral two-level atom trapped in the vicinity of a superconducting body. We derive a simple scaling law for the corresponding spin-flip lifetime for such an atom trapped near a superconducting thick slab. For temperatures below the superconducting transition temperature Tc, the lifetime is found to be enhanced by several orders of magnitude in comparison to the case of a normal conducting slab. At zero temperature the spin-flip lifetime is given by the unbounded free-space value.

An efficient scheme is presented to compute the transverse magnetic susceptibility within time-dependent density functional theory from which magnon dispersions can be extracted. The scheme makes use of maximally localized Wannier functions in order to interpolate the band structure onto a fine k mesh in order to converge sums on the first Brillouin zone. The gap error in the magnon dispersion at , numerically violating Goldstone's theorem, is analyzed and a correction scheme is devised that can be generalized to systems where Goldstone's theorem does not apply. The method is applied to the computation of the magnon dispersion of bulk bcc iron and fcc nickel.

Chemical reactions at metal surfaces are influenced by inherent dissipative processes which involve energy transfer between the conduction electrons and the nuclear motion. We shall discuss how it is possible to model this electron-phonon coupling in order to estimate its importance. A relevant quantity for this investigation is the lifetime of surface-localized electron states. A surface state, quantum well state or surface image state is located in a surface-projected bandgap and becomes relatively sharp in energy. This makes a comparison between calculations and experimental data most attractive, with a possibility of resolving the origin of the lifetime broadening of electron states. To achieve more than an order of magnitude estimate we point out the importance of taking into account the phonon spectrum, electron surface state wavefunctions and screening of the electron-ion potential.