Multiple magnetism controlled topological states in EuAgAs

TL;DR

This study demonstrates how magnetic ordering in EuAgAs can induce multiple topological states, including Dirac, Weyl, and mirror semimetals, revealing rich magnetic control over topological phases.

Contribution

The paper introduces EuAgAs as a material where magnetic configurations can switch between various topological states, expanding the understanding of magnetic topological systems.

Findings

EuAgAs is a Dirac semimetal in the paramagnetic state.

Magnetic ordering induces transitions to Weyl and mirror topological states.

Surface states such as Fermi arcs and Dirac cones are affected by magnetic states.

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.