Physique Théorique des Matériaux, QMAT, CESAM, University of Liège, B-4000, Sart-Tilman, Belgium.
Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
Nat Commun. 2023 Mar 24;14(1):1629. doi: 10.1038/s41467-023-37337-8.
Out-of-plane polar domain structures have recently been discovered in strained and twisted bilayers of inversion symmetry broken systems such as hexagonal boron nitride. Here we show that this symmetry breaking also gives rise to an in-plane component of polarization, and the form of the total polarization is determined purely from symmetry considerations. The in-plane component of the polarization makes the polar domains in strained and twisted bilayers topologically non-trivial, forming a network of merons and antimerons (half-skyrmions and half-antiskyrmions). For twisted systems, the merons are of Bloch type whereas for strained systems they are of Néel type. We propose that the polar domains in strained or twisted bilayers may serve as a platform for exploring topological physics in layered materials and discuss how control over topological phases and phase transitions may be achieved in such systems.
平面外极域结构最近在具有反演对称性破缺的应变和扭曲双层系统（如六方氮化硼）中被发现。在这里，我们表明这种对称性破缺也会导致极化的平面分量，并且总极化的形式完全取决于对称性考虑。极化的平面分量使得应变和扭曲双层中的极域在拓扑上变得非平凡，形成了一系列梅尔和反梅尔（半斯格明子和半反斯格明子）的网络。对于扭曲系统，梅尔是布洛赫型的，而对于应变系统，梅尔是奈尔型的。我们提出，应变或扭曲双层中的极域可能成为探索层状材料中拓扑物理的平台，并讨论如何在这些系统中实现对拓扑相和相变的控制。
