Two-Dimensional Dual-Switchable Ferroelectric Altermagnets: Altering Electrons and Magnons.

Abstract

We predict a new class of two-dimensional (2D) materials, termed dual-switchable ferroelectric altermagnets (FEAMs), where reversing the ferroelectric polarization simultaneously alters both electronic spin splitting and magnonic chirality splitting. This provides a pathway for the unified electrical manipulation of both ground-state electron spin textures and collective magnon excitations within a single monolayer, a largely unexplored area. Employing symmetry analysis and first-principles calculations on five candidates identified via database screening (exemplified by CrPS₃ and V₂I₂O₂BrCl), we elucidate the mechanism in FEAMs. Ferroelectricity driven by specific atomic displacements breaks inversion symmetry while preserving key spin group symmetries (e.g., [C₂||M]). This dual switch could be experimentally observed through a magneto-optical Kerr effect sign change. This work establishes a material-specific pathway toward integrating electrical control over coupled electronic and magnonic properties in two dimensions, paving the way for novel multifunctional spintronic and magnonic applications.