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

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 Moire '-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 as F proportional to theta-32R12, where theta and R are the interfacial twist angle and the radius of the flake, respectively. 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 Moire ' boundary, that is, the remaining part of the twisted layered interfaces after subtracting the internal complete Moire ' supercells. Our work provides new physical insights into the friction origin of layered materials and highlights the importance of Moire ' boundary in the thermodynamic models of layered materials.

Automated summary

Structural superlubricity based on twisted layered materials has attracted significant research interest. Molecular dynamics simulations reveal a strong correlation between the size scaling of friction and Moire '-level oscillations in circular twisted bilayer graphene (tBLG). By proposing a theoretical formula and deriving an analytic expression, we successfully explain the observed abnormal scaling and provide a rational explanation for the measured scattered power scaling law in various experiments. Additionally, we demonstrate that the origin of the scaling law is related to the Moire ' boundary, highlighting its importance in the thermodynamic models of layered materials.