Friction in a single-atom resolution

Friction is a phenomenon that acts on many different length scales. With a sharp nanometer-sized tip, lateral forces can be measured and phenomena like anisotropy or superlubricity can be observed [1, 2]. However, the “large” tip prevents measurements of single chemical bonds. But is this spatial resolution necessary to understand sliding friction? How much does the energy loss differ when sliding over different chemical bonds? We performed lateral force microscopy, in which the tip oscillates laterally above the surface, with small amplitudes and a CO-terminated tip to be directly sensitive to the dissipated energy above single chemical bonds [3]. By comparing the dissipation over different covalent bonds, we found that the local potential energy landscape plays an important role in sliding friction. We were also able to observe dissipation over single O··H bonds. Our findings show that a complete understanding of friction requires a description of the individual chemical bonds at the surface. Then I will also share some recent results aiming the phonon dependent friction measurement.   1. Liley, M. et al., Science, 280(5361), 273-275, (1998).
2. Dienwiebel, M. et al., Physical review letters, 92(12), 126101, (2004).
3. Weymouth, A. J. et al., Physical Review Letters, 124(19), 196101, (2020).