Manifestation of the Dimer Correlation in the Phonon Dispersion of Ge(001)

Abstract

The phonon dispersion of the Ge(001) surface has been calculated using density-functional perturbation theory and local-coupling transfer, which is a novel method for modeling dynamical matrices of large-size superstructures, such as the $c$( $4\ifmmode\times\else\texttimes\fi{}2$) and $p$( $2\ifmmode\times\else\texttimes\fi{}2$) phases. Furthermore, the surface phonons have been determined by inelastic He atom scattering. The measured scattering intensities can be explained only if higher-order reconstructions are assumed, indicating a correlation of the surface dimers with local $c$( $4\ifmmode\times\else\texttimes\fi{}2$) or $p$( $2\ifmmode\times\else\texttimes\fi{}2$) symmetry in Ge(001) at room temperature.