# Surface-Mediated Atomic Geometry and Decoupled States in Short Chains on a Si(553)–Au Surface

## TL;DR

This paper shows how the surface of a material affects the atomic structure and electronic properties of small atom chains.

## Contribution

The study reveals that substrate interactions lead to decoupled electronic states in atom chains.

## Key findings

- Single adatoms show energy-level changes due to substrate interactions.
- Few-atom chains exhibit surface-mediated dimerization and modified electronic states.
- Common STM interpretation methods are challenged for gapped surfaces.

## Abstract

We demonstrate how
the substrate fundamentally shapes atomic-scale systems on its surface
and enables determination of their atomic geometry. Scanning tunneling
microscopy and spectroscopy (STM/STS) measurements, supported by density
functional theory and tight-binding calculations, reveal that even
single adatoms exhibit a convolution with the substrate, leading to
significant energy-level renormalization and a redistribution of their
spectral weight beyond the energy-gapped region. In few-atom chains,
this interaction drives surface-mediated dimerization, modifying both
the geometry and electronic density of states, including the appearance
of decoupled states. We show that, by explicitly incorporating the
substrate’s electronic properties, one can not only reliably
determine the atomic geometry and positions of adsorbed atoms, allowing
for a proper interpretation of STM topography images, but also classify
and assign the origin of the STS spectral peaks. Moreover, our findings
challenge the common substrate dI/dV subtraction methods and the assumption that STM conductance peaks
directly reflect molecular states, an interpretation that is not valid
for gapped or semiconducting surfaces.