Engineering Polar Vortices via Strain Soliton Interactions in Marginally Twisted Multilayer Graphene

Strain solitons have been widely observed in van der Waals materials and their heterostructures. They can manifest as one-dimensional (1D) wires and quasi-two-dimensional (2D) networks. However, their coexistence within the same region has rarely been observed, and their interplay remains unexplored. Here, employing lateral piezoresponse force microscopy, we show that 1D linear solitons and 2D moiré solitons appear simultaneously and interact in twisted multilayer graphene. In twisted monolayer-bilayer graphene, when a linear soliton intersects with moiré solitons, the polarization reverses across the intersections, splitting a polar vortex into two vortices. Interestingly, when a linear soliton is parallel to a moiré soliton, they can annihilate each other in certain case, resulting in the unification of polar vortices. In twisted monolayer-trilayer graphene, linear solitons from different interfaces can be resolved. Our results provide new insights for the interplay between different solitons and pave a new way for engineering moiré physics.