Switching graphitic polytypes in elastically coupled cavities.

Graphitic polytypes-commensurate stacking variants of graphene layers-exhibit pronounced stacking-dependent properties, including intrinsic polarization, orbital magnetism and unconventional superconductivity. Previous attempts to switch between these polytypes required micrometre-scale domains and micronewton loading forces, severely limiting practical multi-ferroic functionality. Here we demonstrate fully reversible transformations of Bernal tetralayers to rhombohedral crystals down to 30-nanometre-scale dimensions, using <1 nanonewton lateral shear forces and an energy of <1 femtojoule per switching event. We achieve this by inserting an intentionally misaligned spacer, patterned by nanometre-scale cavities, between a pair of aligned bilayers. Within each cavity, the active bilayers sag to form stable single-domain polytypes, whereas outside the cavities, the layers slide freely over superlubric, incommensurate interfaces with ultralow friction. Conducting-probe force-microscopy experiments, supported by force-field calculations, reveal edge-nucleated boundary solitons that slide spontaneously to switch the commensurate domains, indicating ultralow pinning and long-range strain relaxations extending tens of nanometres beyond the islands. By engineering cavity geometries, we program elastic coupling between neighbouring islands and tune switching thresholds and trajectories. This reconfigurable slidetronic control establishes a robust route to multi-ferroic response and elastically coupled switching among distinct stacking states.