Unusual topological polar texture in moiré ferroelectrics

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Topological polar textures in ferroelectrics are crucial for advanced data storage.
• Polar merons and antimerons are theoretically predicted in twisted systems but experimentally unconfirmed.
• Twisted two-dimensional van der Waals materials offer a novel platform for exploring exotic electronic phases.

Purpose of the Study:

• To experimentally observe and characterize topological polar textures in twisted 2D van der Waals materials.
• To investigate the nature of polarization patterns at domain walls in these materials.
• To understand the underlying physics governing the formation of these complex polar textures.

Main Methods:

• Vector piezoresponse force microscopy (VPFM) was employed to map polarization fields.
• R-type marginally twisted hexagonal boron nitride was used as the primary material system.
• Theoretical simulations were conducted to interpret experimental observations.

Main Results:

• Experimental observation of a network of polar merons and antimerons in twisted hexagonal boron nitride.
• Identification of alternating out-of-plane polarizations and in-plane vortex-like patterns along domain walls.
• Observation of three polarity reversals across domain walls, attributed to moiré ferroelectricity and piezoelectricity competition.

Conclusions:

• This study provides the first experimental evidence of complex polar textures in moiré ferroelectrics.
• The findings offer new insights into the electronic band topology of twisted transition metal dichalcogenides.
• The observed phenomena pave the way for novel applications in energy-efficient electronics and data storage.