Switchable large-gap quantum spin Hall state in two-dimensional MSi${}_2$Z${}_4$ materials class

Abstract

Quantum spin Hall (QSH) insulators exhibit spin-polarized conducting edge states that are topologically protected from backscattering and offer unique opportunities for addressing fundamental science questions and device applications. Finding viable materials that host such topological states, however, remains a challenge. Here by using in-depth first-principles theoretical modeling, we predict large bandgap QSH insulators in recently bottom-up synthesized two-dimensional (2D) MSi${}_2$Z${}_4$ (M = Mo or W and Z = P or As) materials family with $1T^{\prime }$ structure. A structural distortion in the $2H$ phase drives a band inversion between the metal (Mo/W) $d$ and $p$ states of P/As to realize spinless Dirac cone states without spin-orbit coupling. When spin-orbit coupling is included, a hybridization gap as large as $\sim 204$ meV opens up at the band crossing points, realizing spin-polarized conducting edge states with nearly quantized spin Hall conductivity. We also show that the inverted band gap is tunable with a vertical electric field which drives a topological phase transition from the QSH to a trivial insulator with Rashba-like edge states. Our study identifies 2D MSi${}_2$Z${}_4$ materials family with $1T^{\prime }$ structure as large bandgap, tunable QSH insulators with protected spin-polarized edge states and large spin-Hall conductivity.

7 Pages, 6 Figures, SM is not included

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Cited by in corpus (4)

• Correlation-driven topological transition in Janus VSiGeP2As2
• Fast electrically switchable large gap quantum spin Hall states in MGe${}_2$Z${}_4$
• Mott-Insulator Ca2RuO4 under a static external electric field
• Spin-Hall conductivity and optical characteristics of noncentrosymmetric quantum spin Hall insulators: the case of PbBiI