Topological Weyl Altermagnetism in CrSb

TL;DR

This paper demonstrates that the altermagnet CrSb exhibits a topological Weyl semimetal state with large spin-splitting and spin-polarized Fermi arcs, linking altermagnetism with topological phases of matter.

Contribution

It reveals the topological nature of CrSb as an altermagnetic Weyl semimetal, a novel state combining altermagnetism and topology, driven by large intrinsic spin-splitting.

Findings

Observation of large momentum-dependent spin-splitting up to 1 eV in CrSb

Identification of altermagnetic Weyl nodes with magnetic quantum numbers

Detection of spin-polarized topological Fermi-arcs at the surface

Abstract

Altermagnets constitute a novel, third fundamental class of collinear magnetic ordered materials, alongside with ferro- and antiferromagnets. They share with conventional antiferromagnets the feature of a vanishing net magnetization. At the same time they show a spin-splitting of electronic bands, just as in ferromagnets, caused by the atomic exchange interaction. On the other hand, topology has recently revolutionized our understanding of condensed matter physics, introducing new phases of matter classified by intrinsic topological order. Here we connect the worlds of altermagnetism and topology, showing that the electronic structure of the altermagnet CrSb is topological and hosts a novel Weyl semimetallic state. Using high-resolution and spin angleresolved photoemission spectroscopy, we observe a large momentum-dependent spin-splitting in CrSb, reaching up to 1 eV, that induces altermagnetic Weyl nodes with an associated magnetic quantum number. At the surface we observe their spin-polarized topological Fermi-arcs. This establishes that in altermagnets the large energy scale intrinsic to the spin-splitting - orders of magnitude larger than the relativistic spin-orbit coupling - creates its own realm of robust electronic topology.