Large quantum-spin-Hall gap in single-layer 1T′ WSe2

Chen, P.; Pai, Woei Wu; Chan, Yang-Hao; Sun, Wencong; Xu, Caizhi; Lin, Deng-Sung; Chou, M. Y.; Fedorov, A. V.; Chiang, T.‐C.

doi:10.1038/s41467-018-04395-2

Cited by 140 publications

(134 citation statements)

References 35 publications

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“…16 Furthermore, monolayer WTe 2 is the only member of this materials class that is known to realize the topologically nontrivial 1T structure as its stable ground state. 16,24,25,46 The crystal structure is generated from the tetragonal 1T configuration by a lattice distortion: 16,44,45 the original 1T configuration is composed of three hexagonal layers in rhombohedral ABC stacking with one W layer sandwiched between two Te layers. A structural distortion then shifts the W atoms along the b direction to form zigzag chains.…”

Section: Introductionmentioning

confidence: 99%

Influence of lattice termination on the edge states of the quantum spin Hall insulator monolayer 1T′−WTe2

Lau

Ray

Varjas

et al. 2019

Phys. Rev. Materials

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We study the influence of sample termination on the electronic properties of the novel quantum spin Hall insulator monolayer 1T -WTe2. For this purpose, we construct an accurate, minimal 4-orbital tight-binding model with spin-orbit coupling by employing a combination of densityfunctional theory calculations, symmetry considerations, and fitting to experimental data. Based on this model, we compute energy bands and 2-terminal conductance spectra for various ribbon geometries with different terminations, with and without magnetic field. Because of the strong electron-hole asymmetry we find that the edge Dirac point is buried in the bulk bands for most edge terminations. In the presence of a magnetic field, an in-gap edge Dirac point leads to exponential suppression of conductance as an edge Zeeman gap opens, whereas the conductance stays at the quantized value when the Dirac point is buried in the bulk bands. Finally, we find that disorder in the edge termination drastically changes this picture: the conductance of a sufficiently rough edge is uniformly suppressed for all energies in the bulk gap regardless of the orientation of the edge. II. TIGHT-BINDING MODEL FOR MONOLAYER WTE2WTe 2 is a member of the transition metal dichalcogenide family of materials. Single layers in this materials class crystallize in a variety of polytypic structures such as the hexagonal 2H, the tetragonal 1T , and the distorted 1T structure. 16,44,45 While the former represent trivial semiconductors, the 1T configuration gives rise arXiv:1812.05693v3 [cond-mat.mes-hall]

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Section: Introductionmentioning

confidence: 99%

Influence of lattice termination on the edge states of the quantum spin Hall insulator monolayer 1T′−WTe2

Lau

Ray

Varjas

et al. 2019

Phys. Rev. Materials

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“…Experimental relevance and summary.-Now we briefly discuss the experimental relevance for our proposal. QSHIs with large inverted gaps [44][45][46][47][48][49][50][51][52][53][54][55][71][72][73] in proximity to cuprate or iron-based superconductors [38][39][40][57][58][59][60][61] could provide promising platforms to detect our predictions. For concreteness, we take the inverted InAs/GaSb bilayer and WTe 2 monolayer to estimate µ c x(y) .…”

Section: Arxiv:190509308v1 [Cond-matsupr-con] 22 May 2019mentioning

confidence: 99%

“…This condition indeed corresponds to the QSHI phase with a large inverted gap or equivalently an indirect bulk gap. It is likely realized in the inverted InAs/GaSb bilayer [71][72][73], WTe 2 monolayer [44][45][46][47][48], functionalized MXene [49,50], Bismuthene on SiC [51,52], PbS monolayer [53][54][55], etc. To test the analytical results, we discretize the model (1), put it on a lattice, choose a proper set of parameters (satisfying inequality (8)) and calculate the energy spectrum in a ribbon geometry.…”

Section: Arxiv:190509308v1 [Cond-matsupr-con] 22 May 2019mentioning

confidence: 99%

“…Thus, the Josephson junctions with such a doping-induced 0-π transition provide a novel platform to create or annihilate MBSs by purely electric gating in the absence of φ. These predictions are applicable to a number of candidate systems, including high-temperature QSHIs [44][45][46][47][48][49][50][51][52][53][54][55], in proximity to cuprate or iron-based superconductors.…”

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confidence: 99%

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Detection of second-order topological superconductors by Josephson junctions

Zhang

Trauzettel

2020

Phys. Rev. Research

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We study Josephson junctions based on a second-order topological superconductor (SOTS) which is realized in a quantum spin Hall insulator with a large inverted gap in proximity to an unconventional superconductor. We find that tuning the chemical potential in the superconductor strongly modifies the pairing gap of the helical edge states and leads to topological phase transitions. As a result, the supercurrent in the junction is controllable and a 0-π transition is realized by tuning the chemical potentials in the superconducting leads. These striking features are stable in junctions with different sizes, doping in the normal region, and in the presence of disorder. We propose them as novel experimental signatures of SOTSs. Moreover, the 0-π transition can serve as a fully electric way to create or annihilate Majorana bound states in the junction without magnetic manipulation.Introduction.-The second-order topological superconductor (SOTS) is a novel topological phase of matter and features Majorana zero-dimensional (0D) corner or 1D hinge states which are two dimensions lower than the gapped bulk [1-12] and may provide stable qubits for topological quantum computation [13][14][15][16][17][18][19][20][21]. Recently, the SOTS has been discovered in a variety of realistic materials and triggered tremendous interest [3][4][5][6][7][8][9][10][22][23][24][25][26][27]. One way to mimic SOTSs in 2D is given by quantum spin Hall insulators (QSHIs) in proximity to unconventional superconductors with d x 2 −y 2 -wave or s ± -wave pairing order [3][4][5]. The proximity effect of unconventional superconductivity in 2D systems has also been intensively explored in theory [28][29][30][31][32][33][34][35][36][37] and experiment [38][39][40][41][42][43]. To date, however, the only way proposed to detect 2D SOTSs is a tunneling experiment without a concrete calculation of the observable signature. An alternative or complementary approach to probe SOTSs and manipulate the Majorana corner modes is thus desirable. In QSHIs, a finite doping is usually inevitable, and the chemical potential can be far away from the Dirac points. Therefore, it is interesting and relevant to explore the influence of the chemical potential in SOTSs.

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“…Specifically, the propagation direction of the carriers of the same spin is reversed at the opposite edge. Such unique transport properties enable QSH systems to own promising applications in low-power electronics and spintronics [9][10][11][12] . In the early years, the studies of QSH systems mainly focus on group-VI monolayers (e.g., graphene 1,2 and silicene 13,14 ) and semiconductor quantum wells (e.g., HgTe/CdTe 3,4 and InAs/GaSb 15,16 ).…”

Section: Introductionmentioning

confidence: 99%

Engineering a topological quantum dot device through planar magnetization in bismuthene

Zhou

Cheng

et al. 2019

Phys. Rev. B

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The discovery of quantum spin Hall materials with huge bulk gaps in experiment, such as bismuthene, provides a versatile platform for topological devices. We propose a topological quantum dot (QD) device in bismuthene ribbon in which two planar magnetization areas separate the sample into a QD and two leads. At zero temperature, peaks of differential conductance emerge, demonstrating the discrete energy levels from the confined topological edge states. The key parameters of the QD, the tunneling coupling strength with the leads and the discrete energy levels, can be controlled by the planar magnetization and the sample size. Specially, different from the conventional QD, we find that the angle between two planar magnetization orientations provides an effective way to manipulate the discrete energy levels. Combining the numerical calculation and the theoretical analysis, we identify that such manipulation originates from the unique quantum confinement effect of the topological edge states. Based on such mechanism, we find the spin transport properties of QDs can also be controlled.

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Large quantum-spin-Hall gap in single-layer 1T′ WSe2

Cited by 140 publications

References 35 publications

Influence of lattice termination on the edge states of the quantum spin Hall insulator monolayer 1T′−WTe2

Influence of lattice termination on the edge states of the quantum spin Hall insulator monolayer 1T′−WTe2

Detection of second-order topological superconductors by Josephson junctions

Engineering a topological quantum dot device through planar magnetization in bismuthene

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