Multiple magnetism controlled topological states in EuAgAs

Abstract

The interplay between magnetism and band topology is a focus of current research on magnetic topological systems. Based on first-principle calculations and symmetry analysis, we reveal multiple intriguing topological states can be realized in a single system EuAgAs, controlled by the magnetic ordering. The material is Dirac semimetal in the paramagnetic state, with a pair of accidental Dirac points. Under different magnetic configurations, the Dirac points can evolve into magnetic triply-degenerate points, magnetic linear and double Weyl points, or being gapped out and making the system a topological mirror semimetal characterized by mirror Chern numbers. The change in bulk topology is also manifested in the surface states, including the surface Fermi arcs and surface Dirac cones. In addition, the antiferromagnetic states also feature a nontrivial Z4 index, implying a higher order topology. These results deepen our understanding of magnetic topological states and provide new perspectives for spintronic applications.

The magnetic structure of the topological semimetal Co$_3$Sn$_2$S$_2$

“…A key strategy in the rapidly expanding field of magnetic topological materials is the search for materials which host topological electrons that are strongly coupled to magnetic order. The general aim is to identify systems in which the topological character of the electronic bands can be controlled by altering the spin structure [1][2][3][4][5][6][7].…”