Aubry pinning transition of twisted two-dimensional material bilayers

J Wang and E Tosatti, PHYSICAL REVIEW B, 112, 155406 (2025).

DOI: 10.1103/fmrr-3r5j

The nanomechanical and tribological properties of twisted bilayers of graphene (TBGs) and other two dimensional (2D) structurally lubric interfaces still warrant investigation, particularly about the possibilities of spontaneous, defect-free pinning. We show here through extensive sliding simulations that TBGs remain superlubric even under loads up to 10 GPa and twist angles down to 0.3 degrees, with no evidence of pinning. To understand that, we studied a 2D Frenkel- Kontorova (FK) model-a twisted monolayer lattice in a periodic potential of variable magnitude U-0 and stiffness K. Aubry-type spontaneous pinning appears at small twists, albeit with extra large U-0/Ka(2), when the width w of moir & eacute; dislocations shrinks to similar to 4a, where a is the lattice spacing. A complementary FK-type model based on realistic graphene elasticity and geometry confirms that most TBGs and twisted 2D interfaces lie far below the critical pinning threshold. Their strong in-plane bonds and weak interlayer interactions yield U-0/Ka(2) orders of magnitude too small, and moire dislocations remain wide, w >> a. This provides a unified theoretical framework to understand and predict Aubry pinning transitions, establishing the dislocation width as a practical criterion for spontaneous Aubry pinning, and highlighting its general absence with resilience of sliding lubricity in twisted 2D material bilayers under ordinary conditions.

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