Plasmon-mediated interaction between physically adsorbed atoms — curvature effect

Abstract

The quantum-mechanical formulation of the non-retarded interaction of a single atom with a metallic surface is extended to the study of two neighboring atoms in the presence of a metallic surface. The atoms are represented as fluctuating three-dimensional oscillators, whereas the metal gives a dynamical response through the interaction of the surface plasma oscillations with the external fluctuating dipole. In the total energy balance, one finds, besides the two-body atom-atom and atom-surface interactions, a three-body contribution arising from the surface mediated atom-atom interaction. The flat-surface case is first treated to illustrate how this plasmon-mediated interaction takes place. Then for the general case of two atoms in presence of a curved surface, the three-body interaction term is evaluated. Application is made to the case of a surface having the shape of a spherical particle or a spherical cavity. Numerical evaluation for the case of two argon atoms on solid aluminium has been made in order to determine the relative importance of the modified lateral interaction and the dependence on the radius for the particle or the cavity configuration.