Antiferromagnetic topological insulator in stable exfoliated two-dimensional materials

The antiferromagnetic topological insulator (AFM TI) and two-dimensional (2D) magnet constitute two of the most active fields for hosting prominent physical phenomena and significant advances in novel spintronic devices. However, the 2D AFM TI is scarce. Here, we propose a tight-binding model of the 2D AFM square lattice to demonstrate the emergence of the 2D AFM TI protected by a nonsymmorphic symmetry that is a combination of the twofold rotation symmetry and half-lattice translation. Moreover, based on first-principles calculations, we investigate in total 57 tetragonal antiferromagnets in the crystal structure of outstanding AFM CuMnAs to realize our proposal, and nine experimentally feasible candidates are predicted to be intrinsic 2D nonsymmorphic AFM TIs characterized by the nonzero topological invariant Z(2) = 1 and gapless edge states. The presented results not only greatly extend the scope of magnetic topological states in two dimensions but also put forward potential applications in AFM spintronics.