First-Principles Study On Quantum Anomalous Hall Effect Of 2D Kagome Lattice Zn₂N₃

The quantum anomalous Hall effect characterized by topological invariant Chern number has received a lot of attention from researchers since its realization.Its unique chiral edge state was once considered a key player in the advancement of low-energy spintronic components,and thus the field of quantum anomalous Hall effect materials has become a hotbed of intensive work for numerous people in recent years.Its nearly demanding requirements on the material system greatly limit the temperature at which the effect can be realized.In the early days,the magnetic atom-doped topological insulators Bi₂Te₃and Bi₂Se₃ were only able to realize the quantum anomalous Hall effect at a temperature of 30 m K,which was due to the inhomogeneous magnetic distribution brought about by the doping process,and more and more intrinsic magnetic topological insulators were proposed in subsequent studies.Unfortunately,the highest temperature at which the quantum anomalous Hall effect has been experimentally observed to date has not exceeded 2K,which has undoubtedly posed a great obstacle to subsequent theoretical studies and practical applications.In this context,it is of great interest to propose theoretically more quantum anomalous Hall effect systems with higher realized temperatures.However,studies on how to find such topological non-trivial systems are quite scarce.Many topological non-trivial materials have been discovered in the form of graphene-like structures,such as the famous silicene and germanene,the N atom,which is co-periodic with the C atom,has been excluded from this approach because it cannot form a stable graphene-like structure.Can we find a suitable"scaffold"to force it to form a stable graphene-like structure and then generate topological properties?To investigate the feasibility of such an approach,we propose a two-dimensional Kagome lattice Zn₂N₃in which the N atoms of the graphene-like structure are embedded in a stable"scaffold"composed of Zn atoms.In this paper,we propose a two-dimensional Kagome lattice Zn₂N₃ capable of producing the quantum anomalous Hall effect,and investigate the electronic structure,magnetic properties and topological properties of this system in detail based on first-principles calculations.First,the crystal structure of Zn₂N₃ has been optimized to be totally relaxed,and the calculated lattice constants are a=b=6.45（?）.Its phonon spectrum has been calculated using the density generalized perturbation method under the supercell of 3×3×1,and no imaginary frequency has been found over the whole Brillouin zone,which indicates that Zn₂N₃ has good kinetic stability.Secondly,the energy band structure shows that the splited spin orbitals are completely splited and the spin-down channel has a large band gap of 3.75 e V,while the spin-up channel shows a linear dispersion near the Fermi level and forms a Weyl point at the Fermi level.After further considering the effect of spin-orbit coupling,a tiny band gap of about 4.3 me V is opened at the Weyl point.Meanwhile,the calculation of the magnetic ground state and the magnetic anisotropy energy shows that the system is a ferromagnetic ground state and has a magnetic moment perpendicular to the in-plane.Subsequently,Monte Carlo simulations based on the Heisenberg model estimate the Curie temperature of splited to be about 168 K.Under the combined effect of the band gap generated by the spin-orbit coupling and the out-of-plane magnetic moment,the system will enter the topological non-trivial state.Finally,in order to verify the topological structure of the system,the max localized Wannier function is constructed by matching with the PBE energy band to calculate the key Chern number and quantum anomalous Hall conductance,and the Chern number C and quantum anomalous Hall conductanceσ_xy are obtained as 1 and e²/h,respectively.In addition,the unique chiral edge state is given by constructing the surface Green’s function,the results show that the Chern number,the anomalous Hall conductance,and the chiral edge state all correspond to each other and are logically self-consistent,so it can be said that the topological properties of Zn₂N₃ are real and reliable.In general,it is feasible to use a suitable"scaffold"atom to force the N atom to form a stable graphene-like structure,so the proposed Zn₂N₃ not only expands the material library of quantum anomalous Hall system,but also provides an optional new idea for the search of new topological materials.