Signature of Topological Surface Bands in Altermagnetic Weyl Semimetal CrSb.

As a special type of collinear antiferromagnetism (AFM), altermagnetism has garnered significant research interest recently. Altermagnets exhibit broken parity-time symmetry and zero net magnetization, leading to substantial band splitting in the momentum space. Meanwhile, parity-time symmetry breaking is a prerequisite for nontrivial band topology in Weyl physics. When there is band crossing, it is usually easy to generate Weyl nodes. Weyl semimetal states have been theoretically proposed in altermagnets; rare reports of experimental observation have been made up to this point. Using angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations, we systematically studied the electronic structure of room-temperature altermagnet candidate CrSb. We clearly observed the band spin splitting and signature of topological surface states on the (100) cleaved side surface close to the Fermi level originating from bulk band topology. Our results imply that CrSb contains interesting nontrivial topological Weyl physics, in addition to being an excellent room temperature altermagnet.