Theoretical study of electron states in Au chains on NiAl(110)

TL;DR

This theoretical study uses density functional theory to analyze unoccupied electron resonance states in gold chains on NiAl(110), revealing their origin, interactions, and agreement with experimental data.

Contribution

It introduces a simple tight-binding resonance model to explain adatom interactions and resonance state features in Au chains on NiAl(110).

Findings

Resonance states originate from Au 6s states hybridized with substrate.

The model clarifies adatom interactions and LDOS enhancements.

Calculated band properties agree with experimental spectroscopy.

Abstract

We have carried out a density functional study of unoccupied, resonance states in a single Au atom, dimers, a trimer and infinite Au chains on the NiAl(110) surface. Two inequivalent orientations of the ad-chains with substantially different interatomic distances were considered. From the study of the evolution of the electron states in an Au chain from being isolated to adsorbed, we find that the resonance states derive from the 6$s$ states of the Au atoms, which hybridize strongly with the substrate states and develop a $p$-like polarization. The calculated resonance states and LDOS images were analyzed in a simple tight-binding, resonance model. This model clarifies (1) the physics of direct and substrate-mediated adatom-adatom interactions and (2) the physics behind the enhancements of the LDOS at the ends of the adatom chains, and (3) the physical meaning of the "particle-in-box" model used in the analysis of observed resonance states. The calculated effective mass and band bottom energy are in good agreement with experimental data obtained from scanning tunnelling spectroscopy.