Realizing Abundant Two-Dimensional Altermagnets with Anisotropic Spin Current Via Spatial Inversion Symmetry Breaking.

Altermagnets exhibit nonrelativistic spin splitting with net-zero magnetic moments, making them advantageous for spintronic devices with miniaturized size and high integration. Developing general methods to design altermagnets, particularly in a low dimension, is highly desirable. Here, we propose that breaking the spatial inversion symmetry of crystals can produce altermagnetism in antiferromagnetic monolayers. By applying Janus structurization to two-dimensional (2D) FeSe-type monolayers, 41 polar altermagnets were successfully identified through first-principles calculations, confirming the feasibility of our proposed approach. Furthermore, via systematic screening, we obtained 29 altermagnets with significant spin splitting (>0.5 eV) and high Néel temperatures (above liquid nitrogen temperature). Moreover, using 2D Mn2PSe as an example, we revealed the mechanism of how polarity drives the transformation of antiferromagnets into altermagnets and demonstrated its anisotropic spin current generation and notable spin Hall effect. This work paves a way for realizing high-performance and multifunctional nanoaltermagnets.