title: Unexpected Giant-Gap Quantum Spin Hall Insulator in Chemically Decorated Plumbene Monolayer.
abstract: Quantum spin Hall (QSH) effect of two-dimensional (2D) materials features edge states that are topologically protected from backscattering by time-reversal symmetry. However, the major obstacles to the application for QSH effect are the lack of suitable QSH insulators with a large bulk gap. Here, we predict a novel class of 2D QSH insulators in X-decorated plumbene monolayers (PbX; X = H, F, Cl, Br, I) with extraordinarily giant bulk gaps from 1.03 eV to a record value of 1.34 eV. The topological characteristic of PbX mainly originates from s-p(x,y) band inversion related to the lattice symmetry, while the effect of spin-orbital coupling (SOC) is only to open up a giant gap. Their QSH states are identified by nontrivial topological invariant Z2 = 1, as well as a single pair of topologically protected helical edge states locating inside the bulk gap. Noticeably, the QSH gaps of PbX are tunable and robust via external strain. We also propose high-dielectric-constant BN as an ideal substrate for the experimental realization of PbX, maintaining its nontrivial topology. These novel QSH insulators with giant gaps are a promising platform to enrich topological phenomena and expand potential applications at high temperature.
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhao
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Chang-wen
authors.initials: CW
authors.lastname: Zhang
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Wei-xiao
authors.initials: WX
authors.lastname: Ji
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Run-wu
authors.initials: RW
authors.lastname: Zhang
authors.affiliation: School of Physics, State Key laboratory of Crystal Materials, Shandong University, Jinan, Shandong, 250100, People's Republic of China.
authors.forename: Sheng-shi
authors.initials: SS
authors.lastname: Li
authors.affiliation: School of Physics, State Key laboratory of Crystal Materials, Shandong University, Jinan, Shandong, 250100, People's Republic of China.
authors.forename: Shi-shen
authors.initials: SS
authors.lastname: Yan
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Bao-min
authors.initials: BM
authors.lastname: Zhang
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.affiliation: School of Physics and Technology, University of Jinan, Jinan, Shandong, 250022, People's Republic of China.
authors.forename: Pei-ji
authors.initials: PJ
authors.lastname: Wang
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