Observation of Vortex Domains in a Two-Dimensional Lead Iodide Perovskite Ferroelectric

Topological defects,
such as vortices and skyrmions, provide a
wealth of splendid possibilities for new nanoscale devices because
of their marvelous electronic, magnetic, and mechanical behaviors.
Recently, great advances have been made in the study of the ferroelectric
vortex in conventional perovskite oxides, such as BaTiO3 and BiFeO3. Despite extensive interest, however, no intriguing
ferroelectric vortex structures have yet been found in organic–inorganic
hybrid perovskites (OIHPs), which are desirable for their mechanical
flexibility, ease of fabrication, and low acoustical impedance. We
observed the robust vortex–antivortex topological configurations
in a two-dimensional (2D) layered OIHP ferroelectric (4,4-DFPD)2PbI4 (4,4-DFPD is 4,4-di­fluoro­piper­idinium).
This provides future directions for the study of perovskites and makes
it a promising alternative for nanoscale ferroelectric devices in
medical, micromechanical, and biomechanical applications.

拓扑缺陷（topological defects），诸如涡旋（vortices）与斯格明子（skyrmions），凭借其优异的电子、磁学与力学特性，为新型纳米级器件提供了诸多极具潜力的应用可能。近年来，针对钛酸钡（BaTiO3）、铁酸铋（BiFeO3）等传统钙钛矿氧化物中的铁电涡旋的研究已取得重大进展。尽管学界对此已有广泛关注，但目前尚未在有机-无机杂化钙钛矿（organic–inorganic hybrid perovskites, OIHPs）中发现引人瞩目的铁电涡旋结构——这类材料因其机械柔韧性、制备便捷性以及低声学阻抗而广受青睐。本研究在二维（2D）层状有机-无机杂化钙钛矿铁电体(4,4-DFPD)2PbI4（其中4,4-DFPD即4,4-二氟哌啶鎓）中观测到了稳定存在的涡旋-反涡旋拓扑构型。该发现为钙钛矿领域的研究开辟了全新方向，同时使其有望成为医疗、微机械以及生物力学应用场景中纳米级铁电器件的极具潜力的备选材料。