  Interfacial ferroelectricity emerges in heterostructures consisting of
nonpolar van der Waals (vdW) layers, greatly expanding the scope of two
dimensional ferroelectrics. In particular, the unconventional moire
ferroelectricity observed in bilayer graphene/boron nitride (BN)
heterostructures, exhibits promising functionalities with topological current,
superconductivity and synaptic responses. However, the debate about its
mechanism - correlation driven charge transfer between two graphene layers -
limits device reproducibility and hence large-scale production. Here by
designing a single-layer graphene encapsulated by lattice-mismatched WSe2, we
identify the ferroelectricity as stemming from - instead of graphene moire
bands - the particular BN, where interfacial sliding ferroelectricity must play
a role. With similar structures, multilayer twisted MoS2 is found to reproduce
the ferroelectricity. The key is a conductive moire ferroelectric, where the
screened gate and the pinned domain wall together result in unchanged
electronic states, i.e. anomalous screening. The intimate connection to
interfacial sliding ferroelectricity thus provides advantages of diverse
choices of constituent materials and robust polarization switching while
preserving the unique anomalous screening, paving the way to reproducible and
reliable memory-based devices in artificial intelligence.
