Two-dimensional Dual-Switchable Ferroelectric Altermagnets: Altering Electrons and Magnons

Ferroelectric altermagnets (FEAMs) offer unique magnetoelectric coupling properties by combining the characteristics of both antiferromagnets and ferromagnets, yet their multifunctional electric control remains largely unexplored. Here, we introduce and investigate a scenario for the simultaneous electrical switching of electronic spin and magnonic chirality splitting in two-dimensional FEAMs. Based on the C2DB database, employing symmetry analysis and first-principles calculations, we study prototypical candidates CrPS${}_3$ and V${}_2$I${}_2$O${}_2$BrCl. We identify the mechanism: ferroelectricity arises from asymmetric displacements (P along $z$ in CrPS${}_3$, V along the $xy$-direction in V${}_2$I${}_2$O${}_2$BrCl), which inherently couples electric polarization to both electronic and magnonic degrees of freedom by retaining [C${}_2$$\mathrm{\mid }\mathrm{\mid }$M] symmetry. Our calculations explicitly demonstrate that reversing the ferroelectric polarization concurrently switches the sign of the electronic spin splitting and chirality of magnonic modes. This shows these materials as dual-switchable FEAMs, enabling unified electrical manipulation of electron and magnon properties. A potentially experimentally detectable method via the magneto-optical Kerr effect was derived. This work provides a materials-specific realization and theoretical basis for designing novel electrically controlled multifunctional spintronic, spin caloritronic, and magnonic devices.