INDIRECT INTERACTIONS BETWEEN ADSORBATES IN CONTACT WITH QUASI-ONE-DIMENSIONAL SURFACE ELECTRONIC CHAIN STATES

We consider the screening properties of quasi-one-dimensional electronic states which may occur on low index surfaces (flat or stepped) of some fee 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 eta(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 similar to cos[2k(F)d - 2 eta(a)(epsilon(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.