Two-Dimensional Multiferroics: Ferroelasticity, Ferroelectricity, Domain Wall, and Potential Mechano-Opto-Electronic Applications

TL;DR

This paper predicts that monolayer Group IV monochalcogenides are stable 2D multiferroics with coupled ferroelectricity and ferroelasticity, exhibiting strong optical anisotropy and potential for innovative nanoelectronic and photonic devices.

Contribution

It introduces a new class of stable 2D multiferroic materials with coupled properties and explores their tunability and application potential in advanced device concepts.

Findings

GeS, GeSe, SnS, and SnSe are stable 2D multiferroics at room temperature.

These materials exhibit strong in-plane ferroelectric and ferroelastic coupling.

They have promising applications in tunable memory and photonic devices.

Abstract

Low-dimensional multiferroic materials hold great promises in miniaturized device applications such as nanoscale transducers, actuators, sensors, photovoltaics, and nonvolatile memories. Here, using first-principles theory we predict that two-dimensional (2D) monolayer Group IV monochalcogenides including GeS, GeSe, SnS, and SnSe are a class of 2D semiconducting multiferroics with strongly coupled giant in-plane spontaneous ferroelectric polarization and spontaneous ferroelastic lattice strain that are thermodynamically stable at room temperature and beyond, and can be effectively modulated by elastic strain engineering. Their optical absorption spectra exhibit strong in-plane anisotropy with visible-spectrum excitonic gaps and sizable exciton binding energies, rendering the unique characteristics of low-dimensional semiconductors. More importantly, the predicted low domain wall energy and small migration barrier together with the coupled multiferroic order and anisotropic electronic structures suggest their great potentials for tunable multiferroic functional devices by manipulating external electrical, mechanical, and optical field to control the internal responses, and enable the development of four device concepts including 2D ferroelectric memory, 2D ferroelastic memory, and 2D ferroelastoelectric nonvolatile photonic memory as well as 2D ferroelectric excitonic photovoltaics.