Phase Transition of Moire Edges in Interfacial Ferroelectrics

Z Guan and WC Fan and LQ Wei and W Cao and WY Tong and M Tian and N Wan and WH Sun and BB Chen and PH Xiang and CG Duan and N Zhong, ACS NANO, 19, 39220-39227 (2025).

DOI: 10.1021/acsnano.5c12740

Moire superlattices based on twisted van der Waals (vdW) heterostructures have recently emerged as platforms exhibiting intriguing electrical properties. In particular, interfacial ferroelectricity has been observed in marginally twisted moire superlattices that break the inversion symmetry, exhibiting adjacent domains with opposite polarization. Polarization switching in these systems is mediated by moire edge shifts; however, the underlying physical mechanisms remain poorly understood. In this work, by combining in situ scanning probe microscopy with theoretical modeling, we reveal a phase transition of the moire edge in which its geometry reversibly transforms from convex to concave, accompanied by the splitting of a single domain wall into three. This phase transition can be triggered by localized pressure applied by the probe tip, which induces bending of the moire edge and results in local interlayer sliding. This finding provides a pathway for tuning the electronic properties of moire superlattices by engineering the structure and dynamics of moire edges.

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