2015/10/31 by Liujiang Zhou, Liangzhi Kou, Yan Sun +6 · 128 citations
Chemistry · Materials Science · Physics and Astronomy · #2D Materials and Applications #Band gap #Chemistry #Condensed matter physics #Ferromagnetism #Graphene research and applications #Materials science #Metal #Metal–insulator transition #Monolayer #Nanotechnology #Optoelectronics #Phosphorene #Physics #Semiconductor #Spintronics #Topological Materials and Phenomena #Topological insulator #Transition metal #cond-mat.mtrl-sci
paper · pdf · doi:10.1021/acs.nanolett.5b02617
published in Nano Letters 15(12), 7867-7872 (American Chemical Society) · 4 figures
openalex publication_date 2015/11/02 · arxiv created 2015/12/14 · arxiv updated 2015/12/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Topological insulators (TIs) are promising for achieving dissipationless transport devices due to the robust gapless states inside the insulating bulk gap. However, currently realized two-dimensional (2D) TIs, quantum spin Hall (QSH) insulators, suffer from ultrahigh vacuum and extremely low temperature. Thus, seeking for desirable QSH insulators with high feasibility of experimental preparation and large nontrivial gap is of great importance for wide applications in spintronics. On the basis of the first-principles calculations, we predict a novel family of 2D QSH insulators in transition-metal halide MX (M = Zr, Hf; X = Cl, Br, and I) monolayers, especially, which is the first case based on transition-metal halide-based QSH insulators. MX family has the large nontrivial gaps of 0.12-0.4 eV, comparable with bismuth (111) bilayer (0.2 eV), stanene (0.3 eV), and larger than ZrTe5 (0.1 eV) monolayers and graphene-based sandwiched heterstructures (30-70 meV). Their corresponding 3D bulk materials are weak topological insulators from stacking QSH layers, and some of bulk compounds have already been synthesized in experiment. The mechanism for 2D QSH effect in this system originates from a novel d-d band inversion, significantly different from conventional band inversion between s-p, p-p, or d-p orbitals. The realization of pure layered MX monolayers may be prepared by exfoliation from their 3D bulk phases, thus holding great promise for nanoscale device applications and stimulating further efforts on transition metal-based QSH materials.