Two-Dimensional Multiferroic δ-PbO Monolayer with a Large In-Plane Negative Poisson’s Ratio

Abstract

Two-dimensional (2D) multiferroic materials offer a unique platform for the development of next-generation multifunctional devices. Based on first-principles calculations, a stable 2D configuration of a lead oxide (δ-PbO) monolayer is proposed to realize the multiferroic coupling between ferroelectricity (FE) and ferroelasticity (FA). The δ-PbO monolayer has a spontaneous in-plane polarization of about 2.64 × 10 −10 C/m whose orientation can be reversed by overcoming a low energy barrier of 27.5 meV/atom. The interplay between FE and FA enables the switch of the electric polarization direction by 90°. Moreover, the mechanical properties of the δ-PbO monolayer exhibit significant in-plane anisotropy accompanied by a large negative Poisson's ratio of about −0.68. The coexistence of auxeticity and multiferroicity in this 2D material renders a promising strategy to regulate the mechanical and electronic properties and the interplay between them and thereby concepts for nanoscale devices.

Robust ferroelectricity in low-dimensionalδ-SiX (X = S/Se): a first-principles study

“…Here, the strain is defined as , where a and a 0 are the lattice constants for the strained and unstrained structures, respectively. 43 As shown in Fig. 5(a), for 2D-SiS and 1D-SiS, it was found that both biaxial ( ε x = ε y ) and uniaxial ( ε x ) compressive strains can reduce the relative displacement of the Si atoms with respect to the S atoms with the DM decreasing, resulting in the P s of SiS suppressed effectively.…”