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Recently, an independent membrane of perovskite oxide has been achieved, enabling its deterministic mechanical assembly into twisted homogeneous bilayers. The twisted oxide interface exhibits a non-uniform shear strain pattern, which is determined by the atomic registration system through the strong ionic covalent bonds of this compound family. The twisted ferroelectric material provides unprecedented opportunities to adjust the topological polar landscape, and this coupling is determined by the piezoelectric coupling between the polarization and the Moiré superlattice modulation produced by the large strain gradient. However, the soft-electrolyte phenomenon is a common phenomenon that may generate polar landscapes in non-ferroelectric materials. Here, we report the polarity topology in the twisted membrane of a centrosymmetric compound SrTiO3 (STO). The polar landscape is generated by the piezoelectric-induced polarization driven by the strain modulation triggered by the twist, and is also supported by the machine learning force field based on first-principles calculations. We further demonstrate that the strain and polarization patterns of the top and bottom layers are correlated in a way that breaks inversion and mirror symmetry, which are determined by the emergent chirality brought about by the twist. This discovery brings exciting opportunities for exploring novel physical effects and functionalities. This research was published under the title "Flexoelectrically Induced Polar Topology in Twisted SrTiO3 Membranes" in Advanced Materials.
References:
DOI: 10.1002/adma.202512969
