A topological meron features a non-coplanar structure, whose order parameters in the core region are perpendicular to those near the perimeter. A meron is half of a skyrmion, and both have potential applications for information carrying and storage. Although merons and skyrmions in ferromagnetic materials can be readily obtained via inter-spin interactions, their behaviour and even existence in ferroelectric materials are still elusive. Here we observe using electron microscopy not only the atomic morphology of merons with a topological charge of 1/2, but also a periodic meron lattice in ultrathin PbTiO₃ films under tensile epitaxial strain on a SmScO₃ substrate. Phase-field simulations rationalize the formation of merons for which an epitaxial strain, as a single alterable parameter, plays a critical role in the coupling of lattice and charge. This study suggests that by engineering strain at the nanoscale it should be possible to fabricate topological polar textures, which in turn could facilitate the development of nanoscale ferroelectric devices.

拓扑瓜具有非共面结构，其核心区域中的顺序参数与周边附近的顺序参数垂直。瓜子是天蝎子的一半，两者都有潜在的信息携带和存储应用。尽管可以通过自旋间相互作用轻松获得铁磁材料中的瓜子和天体离子，但它们的行为甚至在铁电材料中的存在仍然难以捉摸。在这里，我们不仅使用电子显微镜观察了拓扑电荷为1/2的瓜子的原子形态，而且还观察到在SmScO ₃上受到拉伸外延应变的超薄PbTiO ₃薄膜中的周期性瓜格基质。相场模拟使瓜的形成合理化，其外延应变作为单个可变参数，在晶格和电荷的耦合中起关键作用。这项研究表明，通过在纳米尺度上工程应变，应该有可能制造拓扑极性纹理，从而可以促进纳米铁电器件的开发。