Polar meron-antimeron networks in strained and twisted bilayers

Area of Science:

• Condensed Matter Physics
• Materials Science
• Topological Physics

Background:

• Out-of-plane polar domain structures observed in strained/twisted bilayers of inversion symmetry broken systems (e.g., hexagonal boron nitride).
• Previous studies focused on out-of-plane polarization, leaving in-plane components unexplored.

Purpose of the Study:

• To investigate the emergence and implications of in-plane polarization in strained and twisted bilayers.
• To explore the topological nature of polar domains arising from symmetry breaking.

Main Methods:

• Symmetry analysis to determine the form of total polarization.
• Identification of topological defects (merons, antimerons) based on polarization components.

Main Results:

• Symmetry breaking in these bilayers induces an in-plane polarization component alongside the out-of-plane component.
• The combined polarization creates topologically non-trivial polar domains, forming networks of merons and antimerons.
• Merons are of Bloch type in twisted bilayers and Néel type in strained bilayers.

Conclusions:

• Strained and twisted bilayers with polar domains serve as a platform for exploring topological physics.
• Potential for controlling topological phases and phase transitions in layered materials.