Discovery of Ultrasmall Polar Merons and Rich Topological Phase Transitions: Defects Make 2D Lead Chalcogenides Flexible Topological Materials,Advanced Functional Materials

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Discovery of Ultrasmall Polar Merons and Rich Topological Phase Transitions: Defects Make 2D Lead Chalcogenides Flexible Topological Materials
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2023-11-30 , DOI: 10.1002/adfm.202311141
Tao Xu ₁ , Tao Qian ₂ , Jie Wang _{3,

4} , Hiroyuki Hirakata ₁ , Takahiro Shimada ₁ , Takayuki Kitamura ₁

Affiliation

Atomic-scale polar topological configurations, such as skyrmions and merons, have garnered enormous interest due to their rich emergent physical phenomena and promising applications in next-generation electronics. Despite recent progress in the exploration of 2D ferroelectrics, isolated polar topological structures in 2D lattices have not yet been explored. Here, an original design principle is proposed to remove the point group limit for polar structures while achieving atomic-scale polar topological structures in non-ferroelectric monolayers caused by defects in 2D materials. The first-principles calculations show that an isolated polar meron with a diameter < 3.0 nm is generated in the deficient lead chalcogenide monolayer, and its formation is attributed to the synergic effects of vacancy-induced radial atomic displacements and symmetry reduction in 2D materials. The emergent polar meron can transform to rich topological configurations under external stimuli or by manipulation of the defect concentrations. Furthermore, this strategy of atomic-scale symmetry breaking via point defect engineering can be applied to a wide variety of 2D materials to induce polar topological structures. This work generalizes the polar topology from perovskite oxides to 2D materials, facilitating exciting opportunities to create high-density topological configurations that enable the exploration of meron/skyrmion-based functional nanodevices.

中文翻译：

超小极性Meron和丰富拓扑相变的发现：缺陷使二维铅硫属化物柔性拓扑材料

原子尺度的极性拓扑结构，例如斯格明子和米子，由于其丰富的新兴物理现象和在下一代电子学中的有前景的应用而引起了人们的极大兴趣。尽管最近在二维铁电体的探索方面取得了进展，但二维晶格中的孤立极性拓扑结构尚未被探索。在这里，提出了一种原始设计原理，以消除极性结构的点群限制，同时在由二维材料缺陷引起的非铁电单层中实现原子级极性拓扑结构。第一性原理计算表明，在缺陷的铅硫族化物单层中生成了直径<3.0 nm的孤立极性半子，其形成归因于空位引起的径向原子位移和二维材料中对称性降低的协同效应。在外部刺激下或通过控制缺陷浓度，新兴的极地半子可以转变为丰富的拓扑结构。此外，这种通过点缺陷工程打破原子尺度对称性的策略可以应用于多种二维材料，以诱导极性拓扑结构。这项工作将极性拓扑从钙钛矿氧化物推广到二维材料，为创建高密度拓扑结构提供了令人兴奋的机会，从而能够探索基于 meron/skyrmion 的功能纳米器件。

更新日期：2023-11-30

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