Driving a GaAs film to a large-gap topological insulator by tensile strain

Zhao, Mingwen; Chen, Xin; Li, Linyang; Zhang, Xiaoming

doi:10.1038/srep08441

Cited by 64 publications

(55 citation statements)

References 34 publications

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“…Starting from graphene [38], many kinds of QSH insulators have been predicted, including graphene with a sandwich structure [39,40], silicene (germanene/stanene) with RHF [41,42], stanene with a dumbbell structure [43][44][45], MoS 2 allotropes [46][47][48][49][50][51][52], and monolayers containing heavy metal atoms (Bi/Sb/Hf) [24,[53][54][55][56]. In the case of particular substrates [57], applying an external field [58], or using hydrogenation/functionalization [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78], the size of those nontrivial bulk gaps can be further increased. Currently, the largest nontrivial bulk gap is 1.08eV found in Bi 2 F 2 monolayer [59,60], which shows that chemical functionalization is a very powerful way to obtain a large nontrivial bulk gap.…”

Section: Introductionmentioning

confidence: 99%

Gallium bismuth halide GaBi-X2 (X = I, Br, Cl) monolayers with distorted hexagonal framework: Novel room-temperature quantum spin Hall insulators

Leenaerts

Kong

et al. 2017

Nano Res.

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Quantum Spin Hall (QSH) insulators with a large topologically nontrivial bulk gap are crucial for future applications of the QSH effect. Among these, group III-V monolayers and their halides with chair structure (regular hexagonal framework, RHF) were widely studied. Using first-principles calculations, we propose a new structure model for the functionalized group III-V monolayers, which consist of rectangular GaBi-X 2 (X=I, Br, Cl) monolayers with a distorted hexagonal framework (DHF).These structures have a much lower energy than the GaBi-X 2 monolayers with chair structure.Remarkably, the DHF GaBi-X 2 monolayers are all QSH insulators, which exhibit sizeable nontrivial band gaps ranging from 0.17 eV to 0.39 eV. Those band gaps can be widely tuned by applying different spin-orbit coupling (SOC) strengths, resulting in a distorted Dirac cone.

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Section: Introductionmentioning

confidence: 99%

Gallium bismuth halide GaBi-X2 (X = I, Br, Cl) monolayers with distorted hexagonal framework: Novel room-temperature quantum spin Hall insulators

Leenaerts

Kong

et al. 2017

Nano Res.

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“…Group V elements, including Bi [28,29], Sb [30] thin films are also found to be large-gap QSH insulators, when functionalized with hydrogen or halogen atoms. More recently, functionalized group III-V materials GaAs and GaBi have also reported to be large-gap QSH insulators [31,32]. These large-gap QSH insulators are essential for realizing many exotic phenomena and for fabricating new quantum devices that can operate at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Ethynyl-functionalized stanene film: a promising candidate as large-gap quantum spin Hall insulator

Zhang

et al. 2015

New J. Phys.

153

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Quantum spin Hall (QSH) effect is promising for achieving dissipationless transport devices which can be achieved only at extremely low temperature presently. The research for new large-gap QSH insulators is critical for their realistic applications at room temperature. Based on first-principles calculations, we propose a QSH insulator with a sizable bulk gap as large as ∼0.22 eV in stanene film functionalized with the organic molecule ethynyl (SnC 2 H), whose topological electronic properties are highly tunable by the external strain. This large-gap is mainly due to the result of the strong spinorbit coupling related to the p xy orbitals at the Γ point of the honeycomb lattice, significantly different from that consisting of the p z orbital as in free-standing group IV ones. The topological characteristic of SnC 2 H film is confirmed by the Z 2 topological order and an explicit demonstration of the topological helical Dirac type edge states. The SnC 2 H film on BN substrate is observed to support a nontrivial large-gap QSH, which harbors a Dirac cone lying within the band gap. Owing to their high structural stability, this two-dimensional large-gap QSH insulator is promising platforms for topological phenomena and new quantum devices operating at room temperature in spintronics.

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“…Additionally, our recent work showed that tensile strain can serve as an effective means to drive a normal insulator to a QSH insulator 21 .…”

Section: Introductionmentioning

confidence: 99%

Hydrogenation-induced large-gap quantum-spin-Hall insulator states in a germanium–tin dumbbell structure

Chen

Zhao

2015

RSC Adv.

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The quantum spin Hall (QSH) effect in two-dimensional topological insulators (2D TIs) is promising for building nanoscaled devices with low energy consumption. The 2D TIs with a bulk band gap larger than the atomic thermal motion energy at room temperature (~26 meV) are essential for achieving room-temperature QSH effects. We proved from first-principles that this goal may be reached in a hydrogenated germanium-tin (Sn 6 Ge 4 H 4 ) dumbbell (DB) structure, where spin-orbit coupling (SOC) opens a bulk band gap of 235 meV. The topological nontriviality is related to the band inversion of s-p xy of Sn atoms induced by surface hydrogenation and can be characterized by a topological invariant of Z 2 =1. This work offers a promising candidate material for achieving long-desired room-temperature QSH effect. / 25equilibrium state, the interlayer spacing between DB Sn 6 Ge 4 H 4 and the substrate is about 2.29 Å, suggesting weak interaction between them. We calculated the electronic band structure of the superstructure and found that the band lines in the vicinity of the Fermi level are in accordance with the free-standing DB Sn 6 Ge 4 H 4 , as shown in Fig. 6(b) and 6(c). Both s-p band inversion and topological nontriviality are intact, except that the SOC bulk gap is slightly improved. The robust topological nontriviality of DB Sn 6 Ge 4 H 4 against substrate effects is related to the origins of the bands near the Fermi level. These bands are mainly contributed by s and p xy atomic orbitals rather than p z orbital and thus are unlikely affected by substrates. ConclusionsUsing first-principles calculations, we demonstrated theoretically that the unique coordinates of the 2D germanium-tin compound with a dumbbell structure (DB Sn 6 Ge 4 ) make it energetically more stable than low-buckled stanene and germanene. DB Sn 6 Ge 4 is a normal insulator with a direct gap of 242 meV. However, upon surface hydrogenation (resulting in DB Sn 6 Ge 4 H 4 ), it converts a QSH insulator characterized by a topological invariant of Z 2 =1. The quantum phase transition from a normal insulator to a QSH insulator is related to the s-p band inversion induced by surface hydrogenation. The bulk band gap opened due to SOC can be as large as 235 meV which is much larger than the thermal motion energy at room temperature (~26 meV).The topological nontriviality is robust against substrate effects. The energetic stability and the phonon spectrum confirm the high stability and plausibility of DB Sn 6 Ge 4 H 4 .These results are beneficial for achieving long-desired room-temperature QSH effect

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Driving a GaAs film to a large-gap topological insulator by tensile strain

Cited by 64 publications

References 34 publications

Gallium bismuth halide GaBi-X2 (X = I, Br, Cl) monolayers with distorted hexagonal framework: Novel room-temperature quantum spin Hall insulators

Gallium bismuth halide GaBi-X2 (X = I, Br, Cl) monolayers with distorted hexagonal framework: Novel room-temperature quantum spin Hall insulators

Ethynyl-functionalized stanene film: a promising candidate as large-gap quantum spin Hall insulator

Hydrogenation-induced large-gap quantum-spin-Hall insulator states in a germanium–tin dumbbell structure

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