  2D intercorrelated ferroelectrics, exhibiting a coupled in-plane and
out-of-plane ferroelectricity, is a fundamental phenomenon in the field of
condensed-mater physics. The current research is based on the paradigm of
bi-directional inversion asymmetry in single-layers, which restricts 2D
intercorrelated ferroelectrics to extremely few systems. Herein, we propose a
new scheme for achieving 2D intercorrelated ferroelectrics using van der Waals
(vdW) interaction, and apply this scheme to a vast family of 2D vdW materials.
Using first-principles, we demonstrate that 2D vdW multilayers-for example, BN,
MoS2, InSe, CdS, PtSe2, TI2O, SnS2, Ti2CO2 etc.- can exhibit coupled in-plane
and out-of-plane ferroelectricity, thus yielding 2D intercorrelated
ferroelectricsferroelectric physics. We further predict that such
intercorrelated ferroelectrics could demonstrate many distinct properties, for
example, electrical full control of spin textures in trilayer PtSe2 and
electrical permanent control of valley-contrasting physics in four-layer VS2.
Our finding opens a new direction for 2D intercorrelated ferroelectric
research.
