Edge energy fluctuation: A unified theory of friction scaling laws in twisted layered material interfaces

RESUMO

Interlayer twisting in van der Waals (vdW) layered materials generates moire superlattices, unlocking unique opportunities for engineering their electronic and mechanical functionalities. Here, building on two key insights - the invariance of the potential energy of complete moire tiles during sliding, and the symmetry-breaking effect induced by the slider edge - we propose the concept of edge energy fluctuation (EEF) and demonstrate that the EEF governs the sliding energy barrier of finite-sized sliders. Interestingly, we found that even at a fixed twist angle and sliding direction, significant frictional anisotropy emerges when the slider edge is cut along different directions, resulting in distinct friction scaling laws. Furthermore, we present a friction engineering paradigm for twisted layered material interfaces through the deliberate introduction of hierarchical edges, offering a promising route for friction control in superlubric devices.