Phonon lineshapes in atom–surface scattering

Abstract

Phonon lineshapes in atom–surface scattering are obtained from a simple stochastic modelbased on the so-called Caldeira–Leggett Hamiltonian. In this single-bath model, theexcited phonon resulting from a creation or annihilation event is coupled to athermal bath consisting of an infinite number of harmonic oscillators, namely thebath phonons. The diagonalization of the corresponding Hamiltonian leads to arenormalization of the phonon frequencies in terms of the phonon friction ordamping coefficient. Moreover, when there are adsorbates on the surface, thissingle-bath model can be extended to a two-bath model accounting for the effectinduced by the adsorbates on the phonon lineshapes as well as their correspondinglineshapes.