Recent theoretical work has predicted the existence of a“dipole spiral”structure in strained freestanding membranes of PbTiO_(3),suggesting a potential route to enhanced electromechanical responses[Phys.Rev.Lett.133...Recent theoretical work has predicted the existence of a“dipole spiral”structure in strained freestanding membranes of PbTiO_(3),suggesting a potential route to enhanced electromechanical responses[Phys.Rev.Lett.133046802(2024)].However,its microscopic nature,energetic landscape,and electronic properties remain largely unexplored from a first-principles perspective.Here,using density functional theory on PbTiO3 under biaxial tensile strain,we identify a novel form of polar order:a chiral,non-collinear ferroelectric double helix.We find that two distinct,intertwined polarization helices are formed by the local Pb-O and Ti-O dipoles,reminiscent of DNA.This topology is stabilized by a collective helical twisting of the encompassing oxygen cages(the polyhedra for both Pb and Ti cations),which gives rise to an electric Dzyaloshinskii–Moriya-like interaction.The resulting structure,which can be conceptualized as a“self-moiré”crystal,exhibits two coupled functionalities.First,it possesses a rotational pseudo-zero-energy mode that underpins a giant piezoelectric response(e_(33)≈16C/m^(2)).Second,the long-period potential reconstructs the electronic band structure,leading to a multi-valley electronic topology at the valence band edge.Our work establishes a physical route to designing complex chiral order that supports both giant electromechanical coupling and multi-valley electronics.展开更多
基金supported by Zhejiang Provincial Natural Science Foundation of China(Grant No.LR25A040004)。
文摘Recent theoretical work has predicted the existence of a“dipole spiral”structure in strained freestanding membranes of PbTiO_(3),suggesting a potential route to enhanced electromechanical responses[Phys.Rev.Lett.133046802(2024)].However,its microscopic nature,energetic landscape,and electronic properties remain largely unexplored from a first-principles perspective.Here,using density functional theory on PbTiO3 under biaxial tensile strain,we identify a novel form of polar order:a chiral,non-collinear ferroelectric double helix.We find that two distinct,intertwined polarization helices are formed by the local Pb-O and Ti-O dipoles,reminiscent of DNA.This topology is stabilized by a collective helical twisting of the encompassing oxygen cages(the polyhedra for both Pb and Ti cations),which gives rise to an electric Dzyaloshinskii–Moriya-like interaction.The resulting structure,which can be conceptualized as a“self-moiré”crystal,exhibits two coupled functionalities.First,it possesses a rotational pseudo-zero-energy mode that underpins a giant piezoelectric response(e_(33)≈16C/m^(2)).Second,the long-period potential reconstructs the electronic band structure,leading to a multi-valley electronic topology at the valence band edge.Our work establishes a physical route to designing complex chiral order that supports both giant electromechanical coupling and multi-valley electronics.
