Surface-State Localization at Adatoms

TL;DR

This study uses scanning tunneling spectroscopy and theoretical modeling to identify and analyze a common adsorbate-induced bound state on Ag(111) and Cu(111) surfaces, revealing how different adatoms affect surface-state lifetimes.

Contribution

It introduces an extended Newns-Anderson model to explain the origin of a common surface resonance and compares the effects of magnetic and non-magnetic adatoms on surface-state properties.

Findings

Native adatoms decrease surface-state lifetime.

Cobalt adatoms do not significantly alter the surface state.

A common adsorbate-induced bound state exists below the surface-state band.

Abstract

Low-temperature scanning tunneling spectroscopy of magnetic and non-magnetic metal atoms on Ag(111) and on Cu(111) surfaces reveals the existence of a common electronic resonance at an energy below the binding energies of the surface states. Using an extended Newns-Anderson model, we assign this resonance to an adsorbate-induced bound state, split off from the bottom of the surface-state band, and broadened by the interaction with bulk states. A lineshape analysis of the bound state indicates that native adatoms decrease the surface-state lifetime, while a cobalt adatom causes no significant change.