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

J. Thomas, C. Bertram, J. Daru, P. Zhou, D. Marx, K. Morgenstern, U. Bovensiepen

Published 2021-01-22Version 1

Microscopic insight into interactions is key for understanding the properties of heterogenous interfaces. We analyze local attraction and repulsion in non-covalently bonded Xe-Cs+ aggregates on Cu(111). By combining two-photon photoemission spectroscopy, scanning tunneling microscopy, and coupled cluster calculations 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+ 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.