Emergent exotic chirality dependent dielectricity in magnetic twisted bilayer system

TL;DR

This paper uncovers how twist-induced inhomogeneity in magnetic twisted bilayer systems leads to emergent gauge fields, chirality-dependent skyrmion patterns, and exotic dielectric properties, advancing the understanding of Moire materials.

Contribution

It reveals the formation of chirality-dependent gauge fields and skyrmion patterns in magnetic twisted bilayers, introducing new mechanisms for topological electronic polarization and magnetoelectric effects.

Findings

Emergence of U(1) gauge fields due to twist in bilayers

Formation of chirality-dependent real-space skyrmions

Observation of exotic chirality-dependent dielectricity

Abstract

Twisted van der Waals bilayers provide an ideal platform to study the electron correlation in solids. Of particular interest is the 30 degree twisted bilayer honeycomb lattice system, which possesses an incommensurate Moire pattern and uncommon electronic behaviors may appear due to the absence of phase coherence. Such system is extremely sensitive to further twist and many intriguing phenomena will occur. In this work, we show that due to the twist induced spatial inhomogeneity of interlayer coupling, there emerges an U(1) gauge field in magnetic transition-metal dichalcogenides (TMD) bilayers. Interestingly, for further twist near 30 degree, the induced gauge field could form a chirality dependent real-space skyrmion pattern, or magnetic charge. Moreover, such twist also induces the topology dependent electronic polarization of the bilayer system through the nonzero flux of the real-space Berry curvature. Further analysis proves that the antiferromagnetically coupled twisted bilayer system is indeed also antiferroelectric! When an external electric field is applied to break the potential balance between layers, there will emerge novel magnetoelectric coupling and exotic chirality dependent dielectricity. Such findings not only enrich our understanding on Moire systems, but also open an appealing route toward functional 2D materials design for electronic, optical and even energy storage devices.