Auxetic and multiferroic MP₅ (M = Al, Ga): a novel 2D material with negative Possion's ratio and high anisotropic...

In the field of materials science, the development of multifunctional 2D materials has been a long-standing research objective. In this study, we employ first-principles calculations to predict a novel 2D material named MP₅ (M = Al, Ga), which exhibits ferroelasticity, ferroelectricity, negative Poisson's ratio, and high anisotropic carrier mobility. Our investigation reveals that a single layer of MP₅ displays multiferroic behavior, wherein ferroelasticity and ferroelectricity are coupled. The remarkable structural anisotropy of MP₅ enables easy switching between ferroelastic and ferroelectric states, rendering it suitable for nonvolatile memory applications. Simultaneously, monolayer AlP₅ (GaP₅) demonstrates a negative Poisson's ratio of -0.074 (-0.058) and a carrier mobility of up to 91 720 cm² V^-1 S^-1 (99 690 cm² V^-1 S^-1). These exceptional properties position monolayer MP₅ as a highly versatile and promising 2D material for implementation in nanomechanical and microelectromechanical devices.