Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 39: Tribology
O 39.4: Vortrag
Mittwoch, 7. September 2022, 11:15–11:30, H6
Dissipative frictional mechanism over Moiré superstructure — •Yiming Song1, Xiang Gao2, Antoine Hinaut1, Sebastian Scherb1, Shuyu Huang1, Oded Hod2, Michael Urbakh2, and Ernst Meyer1 — 1Department of Physics, University of Basel, Basel, Switzerland — 2Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv, Israel.
Friction force microscopy experiments performed on graphene-coated platinum surfaces that exhibit a variety of moiré superstructures demonstrate that, in addition to the well-known atomic stick-slip dynamics, a new dominant energy dissipation mechanism emerges. The observed velocity dependence of friction displays two distinct regimes: (i) at low velocities, the friction force is small and nearly constant; whereas (ii) above some threshold, friction increases logarithmically with velocity. The threshold velocity, separating the two frictional regimes, decreases with increasing normal load and moiré superstructure period. Atomistic molecular dynamics simulations demonstrate that the main contribution to frictional energy dissipation results from the elastic deformation and subsequent relaxation of moiré ridges caused by the pushing action of the tip as it slides over the superstructure. Based on the simulation results we develop a semi-phenomological model, which makes it possible to calculate friction under measurement conditions and provides excellent agreement with the experimental observations.