Quantifying the phononic contribution to friction at the single-atom scale (Phase 2)

• Applicant: Privatdozent Dr. Alfred John Weymouth
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 575917256

The Klimaschutzplan 2050 outlines Germany’s strategy to limit global temperature rise, with increased energy efficiency as a key component. A fundamental yet underexplored aspect of energy efficiency is the role of friction. A complete description of friction depends upon understanding interactions at the atomic scale. In Phase 1 of this project, we investigated the phononic contribution to atomic-scale friction by comparing energy dissipation when a single atom slides over hydrogen (H)-terminated versus deuterium (D)-terminated surfaces. While prior experimental work with atomic force microscopy in contact mode had suggested a significant difference, theoretical studies challenged these findings, attributing them to local defects rather than inherent phononic effects. Using lateral force microscopy (LFM) with oscillation amplitudes smaller than the atomic spacing, we successfully measured energy dissipation over H- and Dterminated surfaces. However, the results were inconclusive due to variations in tip apex structure between the measurements. Phase 2 will address this limitation by employing atomically controlled tips, allowing for precise, reproducible measurements. We will leverage advanced tip characterization techniques developed in Phase 1 to ensure consistency. The outcome of this research will not only resolve the debated role of phononic contributions in friction but also establish a robust methodology for quantifying all atomic-scale dissipation pathways, including electronic contributions. This knowledge will pave the way for engineered materials with tailored frictional properties, contributing to improved energy efficiency across multiple fields.

• DFG Programme: Research Grants
• International Connection: Austria, United Kingdom
• Co-Investigator: Professor Dr. Franz J. Giessibl
• Cooperation Partners: Professor Dr. Oliver T. Hofmann; Dr. Lukas Hörmann