Lateral force modulation by moiré superlattice structure: Surfing on periodically undulated graphene sheets

It has been recently demonstrated that moiré pattern formed between graphene and supporting crystalline substrate can modulate atomic friction [1-3] which provides a novel strategy to control friction at the nanoscale. Despite the high potential of this new approach, its underlying mechanism is still unclear. Using molecular dynamics (MD) simulation, we reveal that moiré pattern induced lateral force modulation arises from geometric undulation of graphene due to its different stacking states on the substrate. As a result, a periodic offset modulation in lateral force is produced when a tip slides over graphene with varying height. Since height undulations could be induced either by weak van der Waals interactions or by stronger semi-covalent bonds in moiré superlattice structures [1,3-5], we expect the revealed mechanism to be generally applicable for explaining lateral force modulation of these two-dimensional heterostructures.

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