Atomically Thin Quantum Spin Hall Insulators

Lodge, Michael S.; Yang, Shengyuan A.; Mukherjee, Shantanu; Weber, Bent

doi:10.1002/adma.202008029

Cited by 44 publications

(50 citation statements)

References 282 publications

(889 reference statements)

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“…Despite the strong hybridization, we find that a measurable enhancement of the measured local density of states persists at the crystal edges, detectable in both the normal state and in a slight enhancement of the order parameter in the superconducting state. We believe that our multi-band treatment of strongly hybridized van-der-Waals heterostructures will form a useful tool to mapping spatial variation of the induced superconducting order parameter in wider range proximitized atomically-thin topological materials [51].…”

Section: Discussionmentioning

confidence: 99%

Multiband superconductivity in strongly hybridized 1T′−WTe2/NbSe2 heterostructures

Tao

Tong

et al. 2022

Phys. Rev. B

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The interplay of topology and superconductivity has become a subject of intense research in condensed matter physics for the pursuit of topologically non-trivial forms of superconducting pairing. An intrinsically normal-conducting material can inherit superconductivity via electrical contact to a parent superconductor via the proximity effect, usually understood as Andreev reflection at the interface between the distinct electronic structures of two separate conductors. However, at high interface transparency, strong coupling inevitably leads to changes in the band structure, locally, owing to hybridization of electronic states. Here, we investigate such strongly proximity-coupled heterostructures of monolayer 1T'-WTe2, grown on NbSe2 by van-der-Waals epitaxy. The superconducting local density of states (LDOS), resolved in scanning tunneling spectroscopy down to 500 mK, reflects a hybrid electronic structure, well-described by a multi-band framework based on the McMillan equations which captures the multi-band superconductivity inherent to the NbSe2 substrate and that induced by proximity in WTe2, self-consistently. Our material-specific tight-binding model captures the hybridized heterostructure quantitatively, and confirms that strong inter-layer hopping gives rise to a semi-metallic density of states in the 2D WTe2 bulk, even for nominally band-insulating crystals. The model further accurately predicts the measured order parameter ∆ 0.6 meV induced in the WTe2 monolayer bulk, stable beyond a 2 T magnetic field. We believe that our detailed multi-band analysis of the hybrid electronic structure provides a useful tool for sensitive spatial mapping of induced order parameters in proximitized atomically thin topological materials.

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Section: Discussionmentioning

confidence: 99%

Multiband superconductivity in strongly hybridized 1T′−WTe2/NbSe2 heterostructures

Tao

Tong

et al. 2022

Phys. Rev. B

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“…The typical characteristic of 2D TIs is the existence of the 1D spin-polarization gapless edge state in the 2D bulk gap, which possesses locked spin momentum and is protected by time reversal symmetry (TRS). Attributed to such features, 2D TIs can suppress backscattering and realize the nondissipative transport of electrons, thus playing a crucial role in the application fields, such as low-power electronics, topological switches, spintronics, and topological superconductivity. , …”

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confidence: 99%

Large Gap Two-Dimensional Topological Insulators with the Significant Rashba Effect in Ethynyl and Methyl Functionalized PbSn Monolayers

Wang

Lei

Wan

et al. 2021

J. Phys. Chem. Lett.

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Two-dimensional (2D) topological insulators (TIs) have recently attracted a great deal of attention due to their nondissipation electron transmission, stable performance, and easy device integration. However, a primary obstacle to influencing 2D TIs is the small bandgap, which limits their room-temperature applications. Here, we adopted first-principles to predict inversion-asymmetric group IV monolayers, PbSn(C 2 H) 2 and PbSn(CH 3 ) 2 , to be quantum spin Hall (QSH) insulators with large topological gaps of 0.586 and 0.481 eV, respectively. The nontrivial band topologies, which can survive in a wide range of strain, are characterized by topological invariants Z 2 , gapless edge states, and the Berry curvature. Another intriguing characteristic is the significant Rashba SOC effect which can also be tuned by feasible compressive and tensile strains. Meanwhile, the hexagonal boron nitride (h-BN) provides a suitable substrate for growth of these films without influencing their topological phases. These novel materials are expected to accelerate the development of advanced quantum devices.

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“… 23 However, the QSH effect has been experimentally verified in only a few 2D materials. 24 The majority of the predicted 2D TIs are pristine or are functionalized in freestanding form with small band gaps. However, 2D materials need to be transferred on a substrate in practical applications and later be integrated into the semiconductor industry.…”

Section: Introductionmentioning

confidence: 99%

Robust Tunable Large-Gap Quantum Spin Hall States in Monolayer Cu₂S on Insulating Substrates

et al. 2022

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Quantum spin Hall (QSH) insulators with large band gaps and dissipationless edge states are of both technological and scientific interest. Although numerous two-dimensional (2D) systems have been predicted to host the QSH phase, very few of them harbor large band gaps and retain their nontrivial band topology when they are deposited on substrates. Here, based on a first-principles analysis with hybrid functional calculations, we investigated the electronic and topological properties of inversion-asymmetric monolayer copper sulfide (Cu 2 S). Interestingly, we found that monolayer Cu 2 S possesses an intrinsic QSH phase, Rashba spin splitting, and a large band gap of 220 meV that is suitable for room-temperature applications. Most importantly, we constructed heterostructures of a Cu 2 S film on PtTe 2 , h-BN, and Cu(111) substrates and found that the topological properties remain preserved upon an interface with these substrates. Our findings suggest Cu 2 S as a possible platform to realize inversion-asymmetric QSH insulators with potential applications in low-dissipation electronic devices.

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Atomically Thin Quantum Spin Hall Insulators

Cited by 44 publications

References 282 publications

Multiband superconductivity in strongly hybridized 1T′−WTe2/NbSe2 heterostructures

Multiband superconductivity in strongly hybridized 1T′−WTe2/NbSe2 heterostructures

Large Gap Two-Dimensional Topological Insulators with the Significant Rashba Effect in Ethynyl and Methyl Functionalized PbSn Monolayers

Robust Tunable Large-Gap Quantum Spin Hall States in Monolayer Cu₂S on Insulating Substrates

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Atomically Thin Quantum Spin Hall Insulators

Cited by 44 publications

References 282 publications

Multiband superconductivity in strongly hybridized 1T′−WTe2/NbSe2 heterostructures

Multiband superconductivity in strongly hybridized 1T′−WTe2/NbSe2 heterostructures

Large Gap Two-Dimensional Topological Insulators with the Significant Rashba Effect in Ethynyl and Methyl Functionalized PbSn Monolayers

Robust Tunable Large-Gap Quantum Spin Hall States in Monolayer Cu2S on Insulating Substrates

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Robust Tunable Large-Gap Quantum Spin Hall States in Monolayer Cu₂S on Insulating Substrates