Mechano-Ferroelectric Coupling: Stabilization Enhancement and Polarization Switching in Bent AgBiP2Se6 Monolayer

Two-dimensional (2D) van der Waals (vdW) ferroelectrics are the core candidates to develop next generation non-volatile storage devices, which highly rely on ferroelectric stability and feasible approaches to manipulate ferroelectric polarization and domain. Here, based on density functional theory calculations, we demonstrate that the bending deformation can not only manipulate the polarization direction and domain size of AgBiP2Se6 monolayer, but also significantly improve the ferroelectric stability. The ordered polarization in the bent AgBiP2Se6 monolayers can be well maintained under the temperature of 200 K from molecular dynamics simulations, in contrast it is broken at only 100 K for the freestanding counterparts. The phenomena can be attributed to the synergic effects from asymmetric strain energy induced by strain gradient and reduced migration barrier of Ag ions from convex to concave surfaces. More interestingly, the ferroelectric bubble can be induced in the monolayer under biaxial compression strain. This mechano-ferroelectric coupling represents a new mechanism and feasible avenue towards stabilizing and polarization flip in 2D ferroelectrics.