The movement and rotation of the van der Waals layer can create interesting physical properties. In a recent paper in Nature Communications, Daniel Bennett, Eric Bousquet and Philippe Ghosez, from the Theoretical Physics of Materials group (Q-MAT, CESAM research unit) at the University of Liège, and collaborators at the University of Cambridge ( UK) shows. The polar moire field in the hBN bilayer induces a non-trivial wave in the field, forming arrayas of merons and antimerons.
In-plane polarization has recently been observed in spherical systems with distortion symmetry such as hexagonal boron nitride and transition metal dichalcogenides such as MoS2. Polarization depends on the junction between the layers, and when the layers are connected, the polarization of the plane can be switched through the gap between the layers, resulting in ferroelectricity.
When there is a cross-polarization or lattice mismatch between the layers, forming a supercell known as a moiré superlattice, there is a local polarization for each different collection, resulting in a lattice of polar domains moires (MPD ). These MPDs have been experimentally shown to produce electrical current, making them a promising choice for nanoscale electronic applications such as information processing and memory storage.
Here, it is shown that the breaking of this symmetry also results in plane polarization components that were previously neglected, and the nature of the total polarization is determined only by observation of the principle. The in-plane aspect of the polarization makes the MPD topologically non-linear and slightly stretched and twisted. In each section, the polarization completes exactly half of the atmosphere and determines the topological element called meron (half-skyrmion).
MPD in a twisted or twisted bilayer forms a regular network of polar merons and antimerons. For reciprocating ones, the polarization enters and leaves the center of the domain (Néel type), while for reciprocating ones, the polarization covers the periphery of the domain (Bloch type). This means that the topological properties of these materials can be controlled by adjusting the layers in different ways.
MPDs in twisted or distorted bilayers can serve as a new platform for engineering and exploring topological physics in two-dimensional materials.
Source: University of Liège
