Origin of the unusual strain morphologies and polar moiré patterns in twisted ferroelectrics
Phys. Rev. B 113, 174118 – Published 19 May, 2026
DOI: https://doi.org/10.1103/n8yj-f1hv
Abstract
Density functional theory calculations are conducted to understand and reveal the origin of the complex shear strain morphology and of the polar Moiré topological pattern recently observed in twisted bilayers. Our first-principles calculations, along with an original analysis of them allowing the decomposition of the forces into the acoustic and optical contributions, point to the occurrence of forces mostly acting on the acoustic-related motions to produce standing waves of shear strain. Such acoustic waves naturally generate a striking self-organization of the shear strains, and hence create a peculiar gradient of these shear strains. A Moiré dipole pattern, consisting of the interpenetrated arrays of vortices and antivortices made of the electric dipoles, then mostly arises due to the coupling of this gradient of the shear strain with the electric dipoles. Results and discussion about harmonic versus nonharmonic effects on the strength of these patterns is also provided.
