Origin of frictional scaling law in circular twist layered interfaces: simulations and theory

TL;DR

This paper develops a theoretical model to explain the size-dependent frictional scaling law in twisted bilayer graphene, linking it to Moiré boundary effects and validating it with molecular dynamics simulations.

Contribution

It introduces a new analytical formula for the frictional size scaling law in twisted layered interfaces, emphasizing the role of Moiré boundaries.

Findings

The scaling law depends on twist angle and Moiré boundary effects.

The theoretical predictions match molecular dynamics simulation results.

The work explains the scattered experimental power scaling laws in layered materials.

Abstract

Structural superlubricity based on twisted layered materials has stimulated great research interests. Recent MD simulations show that the circular twisted bilayer graphene (tBLG) presenting a size scaling of friction with strong Moir\'e-level oscillations. To reveal the physical origin of observed abnormal scaling, we proposed a theoretical formula and derived the analytic expression of frictional size scaling law of tBLG. The predicted twist angle dependent scaling law agrees well with MD simulations and provides a rationalizing explanation for the scattered power scaling law measured in various experiments. Finally, we show clear evidence that the origin of the scaling law comes from the Moir\'e boundary, that is, the remaining part of the twisted layered interfaces after deleting the internal complete Moir\'e supercells. Our work provides new physical insights into the friction origin of layered materials and highlights the importance of accounting for Moir\'e boundary in the thermodynamic models of layered materials.