Stacking-Dependent Interlayer Ferroelectric Coupling and Moiré Domains in a Twisted AgBiP 2 Se 6 Bilayer.

Rotation/twisting of bilayers could induce unprecedented new physics due to stacking-dependent electronic properties and interlayer coupling, such as the superconductivity in twisted bilayer graphene, which can find applications in electronics. However, deep understanding at the atomic/electronic levels is limited by the capability of accurate theoretical simulations. Here, from first-principles simulations, we found that the AgBiP 2 Se 6 bilayer has stacking-dependent ferroelectric ground states due to interlayer polarization coupling. Interlayer ferroelectric coupling is preferred in an AA-stacked AgBiP 2 Se 6 bilayer, but antiferroelectric coupling is preferred in AB- or AC-stacked configurations. The ferroelectric Moiré patterns are thus observed in a twisted AgBiP 2 Se 6 bilayer with ferroelectric (antiferroelectric) interlayer couplings in the AA (AB/AC)-stacked areas. Our work for the first time unveils the effects of twisting/rotation on interlayer polarization coupling and provides a real example of ferroelectric Moiré patterns.