Monolayer and bilayer PtCl 3 : Energetics, magnetism, and band topology

Abstract

<p>Two-dimensional (2D) magnetic materials hosting nontrivial topological states are interesting for fundamental research as well as practical applications. Recently, the topological state of 2D Weyl half-semimetal (WHS) was proposed, which hosts fully spin polarized Weyl points robust against spin-orbit coupling in a 2D ferromagnetic system, and single-layer PtCl3 was predicted as a platform for realizing this state. Here, we perform an extensive search of 2D PtCl3 structures, by using the particle swarm optimization technique and density-functional theory calculation. We show that the desired PtCl3 phase corresponds to the most stable one at its stoichiometry. The 2D structure also possesses good thermal stability up to 600 K. We suggest SnS2 as a substrate for the growth of 2D PtCl3, which has excellent lattice matching and preserves the WHS state in PtCl3. We find that uniaxial strains along the zigzag direction maintain the WHS state, whereas small strains along the armchair direction drives a topological phase transition from the WHS to a quantum anomalous Hall (QAH) insulator phase. Furthermore, we study bilayer PtCl3 and show that the stacking configuration has strong impact on the magnetism and the electronic band structure. Particularly, the AA′ stacked bilayer PtCl3 realizes an interesting topological state—the 2D antiferromagnetic mirror Chern insulator, which has a pair of topological gapless edge bands. Our work provides guidance for the experimental realization of 2D PtCl3 and will facilitate the study of 2D magnetic topological states, including WHS, QAH insulator, and magnetic mirror Chern insulator states.<br></p>