Large surface charge density oscillations induced by subsurface phonon resonances.

A density functional perturbation theory study of Cu(111) surface dynamics and phonon-induced surface charge density (SCD) oscillations shows that the subsurface phonon resonances such as S3, first predicted by embedded-atom methods, trigger large SCD charge-density oscillations, thus explaining the large helium atom scattering intensity from the anomalous longitudinal resonance found in most metal surfaces. The strong coupling between certain phonons and SCD oscillations is shown to have implications in inelastic electron tunneling spectroscopy and other manifestations of electron-phonon interactions at metal surfaces.