Low Ferroelectric Switching Barriers and Stacking-Insensitive Electronic Structures in CrX2 (X = S, Se, Te) Bilayers Enabled by Weak Interlayer Coupling

Abstract

Two-dimensional (2D) ferroelectrics are highly promising for next-generation nonvolatile memory and low-power nanoelectronic devices, owing to their atomic-scale thickness and tunable polarization. Among these, sliding ferroelectricity in artificially stacked nonpolar 2D materials offers a versatile route to achieve switchable polarization across a broad class of layered systems. Here, using first-principles calculations combined with a semiempirical van der Waals (vdW) dispersion correction, we systematically investigated the electronic structure and sliding ferroelectricity of CrX₂ (X = S, Se, Te) bilayers. We uncover a cooperative control mechanism, where the increasing atomic radius and decreasing electronegativity of the chalcogen element (X) jointly modulate both the out-of-plane vdW interactions and the in-plane Cr-3d/X-p_z orbital hybridization. This interplay leads to a dramatic reduction in the polarization switching barrier from 5.47 to 0.18 meV per unit cell as well as a concurrent decrease in out-of-plane polarization from 0.61 pC/m to 0.02 pC/m as X changes from S to Te, primarily driven by weakened interlayer coupling. Moreover, the electronic structures and elastic constants of CrX₂ bilayers remain largely insensitive to stacking configuration, further corroborating the weak interlayer interactions. In the most stable BA stacking, the band gap exhibits a clear elemental dependence, systematically decreasing from 1.44 eV (CrS₂) to 1.05 eV (CrTe₂). These findings highlight a critical synergistic effect between elemental composition and interlayer coupling in modulating 2D ferroelectricity, offering fundamental design principles for future high-density, low-power memory and logic devices.