Interlayer Coupling Induced Ferroelectricity in Bilayer α-As

Ferroelectric (FE) instability in the puckered lattice of arsenic (α-As) is investigated using density functional theory (DFT) calculations. A bilayer (BL) structure with the most stable AA-stacked configuration is found to exhibit spontaneous ferroelectric polarization arising from an intralayer distortion analogous to that observed in α-Bi monolayers. Unlike conventional two-dimensional (2D) ferroelectricity, which is typically driven by sliding-induced charge transfer, the observed polarization in α-As primarily originates from a lattice contraction along the armchair direction caused by inverted band occupation facilitated through interlayer electron hopping. The calculated polarization reaches 0.63 × 10 ^-10 C/m with the associated transition barrier 5.4 meV/u.c., and our molecular dynamics simulations using machine-learned interatomic potential shows the FE ordering persisting up to ~100 K or 300 K under a uniaxial compression of 0% or -4%, respectively. These results provide new insight into distinct mechanism of 2D ferroelectricity governed by interlayer electronic coupling.