High-temperature Dirac half-metal PdCl3: a promising candidate for realizing quantum anomalous Hall effect

Abstract

The prospect of a Dirac half-metal (DHM) and the realization of the quantum anomalous Hall effect (QAHE) on a honeycomb lattice without external fields are a great challenge in experiments due to the structural complexities of two-dimensional (2D) crystals. Here, based on density-functional theory calculations, we propose an ideal candidate material for realizing these exotic quantum states in a 2D honeycomb metal–halogen lattice, single-layer PdCl₃. We find that the ground state of PdCl₃ is a 100% spin-polarized DHM with a ferromagnetic Curie temperature T_C = 528 K predicted from Monte Carlo simulations. Upon including spin–orbit coupling (SOC), PdCl₃ reveals the QAHE due to the splitting of the manifold of Pd |d_xz〉 and |d_yz〉 bands near the Fermi level, which is characterized by the nontrivial Chern number (C = −1) and chiral edge states. In particular, the origin of the topological properties of the PdCl₃ honeycomb lattice is explained by the tight-binding model. The sensitivity of nontrivial topology to the cooperative effect of the electron correlation of Pd-4d electrons and SOC is demonstrated: when increasing the on-site Coulomb repulsion U, a sizable nontrivial band gap E_g = 68.6 meV is obtained. Additionally, we explore the mechanical and dynamical stability, as well as strain response of PdCl₃ for possible epitaxial growth conditions in experiments. The coexistence of a high temperature DHM and the QAHE in PdCl₃ presents a promising platform for the emerging area of spintronics devices with dissipationless edge states.