Intrinsic quantum anomalous Hall effect and layer-dependent topological state in two-dimensional single-atom-thick honeycomb-Kagome Ta2N6C3

Abstract

Two-dimensional (2D) honeycomb-Kagome lattices endowed with outstanding physical properties have attracted widespread attention in recent years. By using the first-principles calculations, we investigate the electronic, magnetic, and topological properties of a metal-organic framework, namely, 2D single-atom-thick honeycomb-Kagome Ta2N6C3. It is found that the Ta2N6C3 monolayer (ML) exhibits excellent dynamic, thermal, and mechanical stabilities, as can be confirmed by the phonon spectra, molecular dynamics simulations, and elastic constants calculations, respectively. Remarkably, 21.7 meV/f.u magnetic anisotropy energy and 338 K high Curie temperature are obtained in the Ta2N6C3 ML. In the absence of spin–orbit coupling (SOC), the Ta2N6C3 ML belongs to the half-semimetal with a fully spin-polarized linear band crossing at a high-symmetry K/K′ point around the Fermi level. In the presence of SOC, however, the Ta2N6C3 ML should transform into an intrinsic quantum anomalous Hall (QAH) insulator with a 0.18 eV bulk gap and a nonzero Chern number |C| = 1. The nontrivial topology of the Ta2N6C3 ML originates from the strong SOC effect of the dxz/dyz states for the heavy-element Ta atom. Interestingly, with the increase in the layer number for A–A stacked Ta2N6C3, the abundant nontrivial states including QAH, quantum spin Hall, and topological semimetals induced by distinct interlayer coupling appear successively. Finally, the nontrivial topology of the Ta2N6C3 ML has been proven to be robust against the in-plane strain, Hubbard interaction, and insulating substrate for the first time. As expected, hexagonal boron nitride should be a perfect encapsulation substrate for the remaining intrinsic QAH state of the Ta2N6C3 ML. Overall, the obtained results demonstrate that the proposed single-atom-thick honeycomb-Kagome Ta2N6C3 should be a novel, interesting, and desirable platform for future spintronic applications.