Axion insulator, Weyl points, quantum anomalous Hall effect, and magnetic topological phase transition in Eu3In2As4

The magnetic topological phases attract much interest, such as the axion insulator, higher-order topology, Weyl semimetals, and the quantum anomalous Hall effect (QAHE). Here, we predict that the axion insulator phase, magnetic Weyl points, and QAHE can be achieved in ${\mathrm{Eu}}_{3}{\mathrm{In}}_{2}{\mathrm{As}}_{4}$. Recently, single-crystal ${\mathrm{Eu}}_{3}{\mathrm{In}}_{2}{\mathrm{As}}_{4}$ was successfully synthesized, and it exhibits an antiferromagnetic (AFM) ground state. Our first-principles calculations show that it lies on the phase boundary between multiple magnetic topological phases, and the magnetic anisotropy is weak, with an energy difference less than 1 meV. In the AFM state, it can be tuned to an axion insulator by tensile strain. The quantized axion angle $\ensuremath{\theta}=\ensuremath{\pi}$ and the magnetic higher-order topology are characterized by the parity index ${Z}_{4}=2$. By applying an external magnetic field, the induced ferromagnetic (FM) state becomes an ideal magnetic topological semimetal with a single pair of Weyl points or a nodal ring. The QAHE can be achieved in FM multilayer films of ${\mathrm{Eu}}_{3}{\mathrm{In}}_{2}{\mathrm{As}}_{4}$ on a magnetic insulating substrate.