Distinct moir\'e textures of in-plane electric polarizations for distinguishing moir\'e origins in homobilayers

TL;DR

This paper reveals that in-plane and out-of-plane electric polarizations in moiré patterns of 2D bilayers can be used to distinguish their origins, with topologically nontrivial textures arising from local stacking variations.

Contribution

It introduces the concept of in-plane electric polarization textures in moiré patterns as a novel method to identify their formation mechanisms.

Findings

In-plane electric polarizations can be comparable to out-of-plane ones in certain stacking configurations.

Different moiré origins produce distinct topological polarization textures such as merons and anti-merons.

Electric polarization textures can be engineered through twisting and heterostrain combinations.

Abstract

In binary compound 2D insulators/semiconductors such as hexagonal boron nitride (hBN), the different electron affinities of atoms can give rise to out-of-plane electric polarizations across inversion asymmetric van der Waals interface of near 0-degree twist angles. Here we show that at a general stacking order where sliding breaks the in-plane C3 rotational symmetry, the interfacial charge redistribution also leads to an in-plane electric polarization, with a comparable magnitude to that of the out-of-plane ones. The effect is demonstrated in hBN bilayers, as well as in biased graphene bilayers with the gate-controlled interlayer charge redistribution. In long wavelength moir\'e patterns, the in-plane electric polarizations determined by the local interlayer stacking registries constitute topologically nontrivial spatial textures. We show that these textures can distinguish moir\'e patterns of different origins from twisting, biaxial- and uniaxial-heterostrain, where vector fields of the electric polarizations feature Bloch-type merons, N\'eel-type merons, and anti-merons, respectively. Combinations of twisting and heterostrain can further be exploited for engineering various electric polarization textures including 1D quasiperiodic lattices.