Magnetic topological Dirac semimetal transition driven by SOC in EuMg2Bi2

Magnetic topological semimetals have been at the forefront of condensed matter physics due to their ability to exhibit exotic transport phenomena. Investigating the interplay between magnetic and topological orders in systems with broken time-reversal symmetry is crucial for realizing non-trivial quantum effects. In this work, we delved into the electronic structure of the rare-earth based antiferromagnetic Dirac semimetal EuMg2Bi2 using first-principles calculations and angleresolved photoemission spectroscopy. Our calculations revealed that the spin-orbit coupling (SOC) in EuMg2Bi2 prompts an insulator to topological semimetal transition, with the Dirac bands protected by crystal symmetries. Linear dispersive states near the Fermi level, primarily originating from Bi 6p orbitals, were observed on both the (001) and (100) surfaces, confirming that EuMg2Bi2 is a three-dimensional (3D) topological Dirac semimetal. This research offers pivotal insights into the interplay between magnetism, SOC and topological phase transitions in spintronics applications.