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Abstract:
MoS2, one of the transition metal dichalcogenides (TMDs), has gained a
lot of attention due to its excellent semiconductor characteristics and
potential applications. Here, based on density functional theory
methods, we predict a novel 2D QSH insulator in the porous allotrope of
monolayer MoS2 (g-MoS2), consisting of MoS2 squares and hexagons. g-MoS2
has a nontrivial gap as large as 109 meV, comparable with previously
reported 1T'-MoS2 (80 meV) and so-MoS2 (25 meV). We demonstrate that the
origin of the 2D QSH effect in g-MoS2 originates from the pure d-d band
inversion, different from the conventional band inversion between s-p,
p-p or d-p orbitals. The new polymorph greatly enriches the TMD family
and its stabilities are confirmed using phonon spectrum analysis. In
particular, its porous structure endows it with the potential for
efficient gas separation and energy storage applications.
