The ambivalent competition of Coulomb and van-der-Waals interactions in Xe-Cs+ aggregates on Cu(111) surfaces

TL;DR

This study investigates the complex interplay of Coulomb and van-der-Waals forces in Xe-Cs+ aggregates on Cu(111), revealing how xenon influences electrostatic interactions and electron distribution at the interface.

Contribution

It provides a detailed microscopic analysis combining experimental and theoretical methods to explain the ambivalent attraction and repulsion phenomena in Xe-Cs+ systems on Cu(111).

Findings

Xe induces local attraction in Cs+ aggregates.

Xenon causes repulsion of Cs 6s electrons from Cu(111).

The Coulomb interaction's role is crucial in these heterogenous interfaces.

Abstract

Microscopic insight into interactions is a key for understanding the properties of heterogenous interfaces. We analyze local attraction in non-covalently bonded Xe{Cs+ aggregates and monolayers on Cu(111) as well as repulsion upon electron transfer. Using two-photon photoemission spectroscopy, scanning tunneling microscopy, and coupled cluster calculations combined with an image-charge model we explain the intricate impact Xe has on Cs+/Cu(111). We find that attraction between Cs+ and Xe counterbalances the screened Coulomb repulsion between Cs+ ions on Cu(111). Furthermore, we observe that the Cs 6s electron is repelled from Cu(111) due to xenon's electron density. Together, this yields a dual, i.e., attractive or repulsive, response of Xe depending on the positive or negative charge of the respective counterparticle, which emphasizes the importance of the Coulomb interaction in these systems.