Interlayer rotation (twisting) switches interlayer mobility in moiré superlattices

Mobility of mechanical contacts is widely attributed to atomic structures at the interface between contacting bodies. Matching (commensurate) interfacial structures are thought to reduce mobility, while mismatched (incommensurate) structures are thought to increase mobility. Despite its wide acceptance, direct observation of such structure-properties relationships remains elusive today due to limited microscopy access to atomic motions at buried interface between two bodies. Here, we capture key structural transitions linking interfacial mismatch and mobility in real-time by following twisting and sliding dynamics in bilayer moiré nanoflakes of MoS₂ with atomically resolved transmission electron microscopy. The atomic motions show that slippery, mismatched interfaces-unlike sticky, matching interfaces-exhibit distinct dynamical signatures, such as tenfold increase in interfacial mobility and desynchronized atomic motions.