Two-dimensional crossover and strong coupling of plasmon excitations in arrays of one-dimensional atomic wires

TL;DR

This study investigates plasmon excitations in gold atomic wire arrays on silicon surfaces, revealing two-dimensional effects and inter-wire coupling through advanced spectroscopy and microscopy techniques.

Contribution

It provides new insights into the plasmon dispersion and electron density modulation in gold wire arrays, highlighting two-dimensional effects and wire coupling beyond nearest neighbors.

Findings

Plasmon dispersion depends on structural motif and terrace width.

Electron density is modulated on each terrace.

Evidence of coupling between wires beyond nearest neighbors.

Abstract

The collective electronic excitations of arrays of Au chains on regularly stepped Si(553) and Si(775) surfaces were studied using electron loss spectroscopy with simultaneous high energy and momentum resolution (ELS-LEED) in combination with low energy electron diffraction (SPA-LEED) and tunneling microscopy. Both surfaces contain a double chain of gold atoms per terrace. Although one-dimensional metallicity and plasmon dispersion is observed only along the wires, two-dimensional effects are important, since plasmon dispersion explicitly depends both on the structural motif of the wires and the terrace width. The electron density on each terrace turns out to be modulated, as seen by tunneling spectroscopy (STS). The effective wire width of 7.5\,\AA\ for Si(553)-Au -- 10.2\,\AA\ for Si(775)-Au -- , determined from plasmon dispersion is in good agreement with STS data. Clear evidence for coupling between wires is seen beyond nearest neighbor coupling.