Two-dimensional Cr-based kagomé family with extraordinary magnetic and topological property

Two-dimensional (2D) materials incorporating a kagomé lattice provide a unique platform to explore some physical phenomena, but they are relatively rare. Herein, we theoretically propose a family of 2D Cr-based kagomé materials (Cr3XY7, X = S, Se, Te, and Y = F, Cl, Br, I), which are both dynamically and thermodynamically stable. Throughput analysis of the magnetocrystalline anisotropy energy (MAE) and the possible magnetic configurations show that most of them look like 2D Ising ferromagnets, while Cr3TeF7 is like an XY ferromagnet. Moreover, Cr3TeBr7 is an ideal candidate to verify the Mermin–Wagner theorem due to its negligible MAE. More interestingly, three neighboring magnetic moments capped by a Te atom in Cr3TeCl7 are ferromagnetically coupled with each other, and then these trimers will form an inverse in-plane triangular spin configuration at an angle of 120° with Seff = 9/2. For Cr3XY7, their flatbands show very weak dispersion, and the Dirac cones will open a gap due to the breaking anisotropy. However, van Hove singularities at M point still remain intact. In addition, Berry curvatures of single isolated Dirac bands show the opposite and identical symbols at K and K′ points for Cr3SCl7 and Cr3XCl7 (X = Se and Te), respectively, further indicating that they are very promising candidates for valleytronics.