Tunable spin-valley states in collinear-antiferromagnetic Janus Re2X3Y3 (X, Y = I, Br, Cl; X ≠ Y) monolayers

The unconventional spin-valley states in the collinear-antiferromagnetic (AFM) Janus Re2X3Y3 (X, Y = I, Br, Cl; X ≠ Y) monolayers are predicted using effective k · p and tight binding models, which are few reports on two-dimensional AFM systems. The Janus Re2X3Y3 systems with built-in electric fields along the axis of rotation do not lack PT symmetry. Considering spin–orbit coupling, non-highly spin degenerate valleys will spontaneously polarize. The valley polarization of the collinear-AFM hexagonal lattice is effectively adjusted through strain engineering, achieving strong correlations between strain and valley physics in 2D antiferromagnets. However, an interesting single valley state is also observed in the Janus Re2X3Y3 monolayers, which is due to the fact that high tensile strain alters the next-nearest neighbor hopping of Re atoms, resulting in an increase in AFM interaction. In addition, the unique symmetry of the dimer sublattice leads to unusual band structures, further triggering interesting Berry curvature distributions (zero at the K/K′ point), breaking the previous understanding that only exists in bilayer systems. These physical properties of collinear-AFM Janus Re2X3Y3 systems can be expected to replace ferromagnets as the material foundation of spintronics.