Measuring sliding friction at the single atom scale

• Applicant: Privatdozent Dr. Alfred John Weymouth
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 529680507

Recently, we used lateral force microscopy (LFM) to investigate small organic molecules adsorbed on a metal surface. Because LFM was performed at low temperature, the tip apex could be engineered to end in a single well-defined atom. We discovered that when we picked up a single carbon monoxide (CO) molecule, we were sensitive to the energy dissipated as we slid laterally over pairs of surface atoms. This was the first atomically-controlled realization of the Prandtl-Tomlinson model of sliding friction at the single atom level, and an amazingly sensitive measurement: The vertical dependence of the energy dissipation is over ten times more sensitive than that of the tunneling current in scanning tunneling microscopy. The proposed work in this grant application centres around our unique ability to directly observe energy dissipation with an atomically-characterized single-atom asperity. I propose performing fundamental studies of friction and exploring the use of this energy dissipation as a measurement technique. To measure friction in the framework of the Prandtl-Tomlinson model, we are going to perform measurements at various velocities, and with different stiffnesses of the probe particle. We are also going to incorporate simultaneous measurements of vertical forces as well as lateral forces with the same sensor operating at low temperature. We will continue to work with our theoretical collaborators to establish methods to simulate macroscopic friction from an atomic starting point.

• DFG Programme: Research Grants
• International Connection: Austria
• Cooperation Partner: Professor Dr. Oliver T. Hofmann
• Co-Investigator: Professor Dr. Franz J. Giessibl