Multiferroicity in two-dimensional III–V indium pnictide optoelectronic materials†

Three-dimensional (3D) III–V semiconductors including indium pnictides are widely used in optoelectronic devices, such as light-emitting diodes, laser diodes and photodetectors, in their bulk or thin-film geometries. On the other hand, two-dimensional (2D) atomic crystals such as graphene, phosphorene, and transition metal dichalcogenides are promising candidates for next generation optoelectronic technologies. Here, we designed a type of III–V indium pnictide 2D material that can be exfoliated and rebuilt from bulk wurtzite structures, which show benign stability and intriguing physical properties, including in-plane ferroelectricity/antiferroelectricity with low transition barriers (0.01–0.31 eV f.u.⁻¹), direct/quasi-direct band gaps (HSE + SOC: 1.498–2.852 eV), ferroelasticity (2.86–11.90% elastic deformation), switchable hidden spin polarization and spin splitting (31 meV), as well as controllable in-plane negative Poisson's ratio (∼−0.51). Our study suggests a new class of optoelectronic materials that combines the advantages of the well-studied 3D III–V semiconductors and 2D atomic crystals and offers a platform to study the interplay of optoelectronic properties with multiferroic, spintronic, and mechanical properties for the development of miniaturized multifunctional optoelectronic devices.