Anisotropic Spin Transport Enhanced by Zero‐Dimensional Weyl Nodes in Altermagnetic Weyl Semimetals

Abstract The altermagnetic phase is a newly discovered magnetic state, distinguished by a collinear compensated spin configuration, which fundamentally deviates from traditional antiferromagnetic ordering. In this study, a novel topological altermagnet is introduced featuring a distinctive altermagnetic ordering and multiple zero‐dimensional (0D) Weyl nodes, thereby defining it as an altermagnetic Weyl semimetal. Using Mn 4 (PO 4 ) 3 crystal (magnetic space group 122.337) as a case study, it is discovered that its altermagnetic configuration reveals two distinct spin channels accompanied by pronounced transport anisotropy. Crucially, the symmetry‐protected Weyl points (WPs) endowed with quantized topological charges bolster the anisotropic spin transport, with the chiral topology of WPs ensuring robust spin‐momentum locking. Uniquely, this altermagnetic Weyl semimetal generates spin‐selective surface arc states via chiral polarization of WPs, a distinctive feature absent in antiferromagnetic Weyl analogues. The research not only aids in comprehending interplay between altermagnetism and topological states, but also offers a material plateau for the design of energy‐efficient topological spintronic devices.