Competition between Coulomb and van der Waals Interactions in Xe-Cs+ Aggregates on Cu(111) Surfaces

Thomas, J. and Bertram, C. and Daru, J. and Patwari, J. and Langguth, I. and Zhou, P. and Marx, D. and Morgenstern, K. and Bovensiepen, U.

Volume: 127 Pages:
DOI: 10.1103/PhysRevLett.127.266802
Published: 2021

Microscopic insight into interactions is a key for understanding the properties of heterogenous interfaces. We analyze local attraction in noncovalently 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. © 2021 American Physical Society.

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