Electric-Field-Induced Switchable Two-Dimensional Altermagnets

Altermagnetism, as a recently discovered unconventional antiferromagnetism, allows the lifting of spin degeneracy without net magnetization. The spin splitting of the intrinsic altermagnets is protected by the spin space group symmetry and is therefore difficult to control externally. Here, we propose an extrinsic altermagnet as a complement to the intrinsic altermagnet, whose spin splitting is induced by and can be significantly modulated by the electric field. We then screened intrinsic and extrinsic altermagnets by combining symmetry analysis and high-throughput calculations, identifying 16 intrinsic altermagnets and 24 extrinsic altermagnets. We demonstrate that the spin splitting of extrinsic altermagnets is proportional to the electric field strength, and its sign can be switched by reversing the electric field. Some extrinsic altermagnets exhibit considerable spin splitting, such as CaMnSi with 398 meV under an electric field of 0.1 V/& Aring;. This work provides a realistic material platform for the potential application of 2D altermagnets.