Indirect interactions between adsorbates in contact with quasi-one-dimensional surface electronic chain states

Abstract

We consider the screening properties of quasi-one-dimensional electronic states which may occur on low index surfaces (flat or stepped) of some fcc metals as localized chain states. Motivated by the analysis of experimental data on the H/Ni(110) system, we discuss the possible contributions to indirect interactions between two H adatoms which are mediated by such states. We first show in the linear model of screening that these interactions should exhibit long range oscillations which scale as d −1 for large distances d between the adatoms. We use experimental data for the indirect interactions in H/Ni(110) systems to obtain an order of magnitude estimate of parameters involved. It turns out that a relatively large phase shift η a is required for such oscillations. We therefore also use a nonlinear model for the screening of adatoms, based on the Anderson Hamiltonian. This model yields an indirect interaction between two adatoms which is regular for all d and behaves asymptotically as ∼cos[2k F/d − 2η a(ε F)]d where k F is the Fermi wavevector at the metal surface. The physical significance of the parameters of the model derived thereof is discussed in the context of incomplete screening of H adatoms by quasi-one-dimensional electronic chain states existing on the substrate surface.