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New Family of Quantum Spin Hall Insulators in Two-dimensional Transition-Metal Halide with Large Nontrivial Band Gaps
journal contribution
posted on 2015-12-09, 00:00 authored by Liujiang Zhou, Liangzhi Kou, Yan Sun, Claudia Felser, Feiming Hu, Guangcun Shan, Sean C. Smith, Binghai Yan, Thomas FrauenheimTopological 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.
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Keywords
band inversion2 D QSH effectdissipationless transport devicesQSH insulatorsnontrivial gapsQuantum Spin Hall Insulatorsnontrivial gapnanoscale device applicationsbulk gapQSH layersLarge Nontrivial Band GapsTopological insulatorseV2 D QSH insulatorsultrahigh vacuumNew Familytopological insulatorsbulk compounds3 D bulk phasesMX familygapless states3 D bulk materialsMX monolayersnovel familyTI