Recent Advances in Topological Quantum Materials by Angle-Resolved Photoemission Spectroscopy

Chen, Yujie; Gu, Xing; Li, Yiwei; Du, X.; Yang, Lexian; Chen, Yulin

doi:10.1016/j.matt.2020.07.007

Cited by 22 publications

(7 citation statements)

References 151 publications

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“…[38] Using laser-based ARPES with high momentum and energy resolution (Δk = 0.003 Å −1 , ΔE = 3 meV), we observed the signature of the expected surface Dirac point in the fine Fermi surface mapping, as shown in the zoom-in momentum area near Γ (see Figure 3e The tunable excitation energy (hν) and polarization of incident photons in the synchrotron-based ARPES measurements (see Figure 4a) enable us to discriminate band orbitals with different symmetries along the ΓZ direction. [44] Using photon energies of 84 and 99 eV, we measured the band dispersion along Y Y − Γ − (see Figure 4b-i) and Y Z Y − − (see Figure 4b-ii), respectively, which is consistent with corresponding calculations. According to the matrix element effect, orbitals of odd (even) symmetry with respect to the mirror plane defined by the incident light and emission electron are visible under linear vertical (linear horizontal) polarized light with the electric field out of (in) the mirror plane (see detailed discussion in Note S3, Supporting Information).…”

Section: Resultssupporting

confidence: 85%

“…The tunable excitation energy ( hν ) and polarization of incident photons in the synchrotron‐based ARPES measurements (see Figure a) enable us to discriminate band orbitals with different symmetries along the ΓZ direction. [ 44 ] Using photon energies of 84 and 99 eV, we measured the band dispersion along

\overline Y - \overline \Gamma - \overline Y

(see Figure 4b‐i) and

\overline Y - Z - \overline Y

(see Figure 4b‐ii), respectively, which is consistent with corresponding calculations. According to the matrix element effect, orbitals of odd (even) symmetry with respect to the mirror plane defined by the incident light and emission electron are visible under linear vertical (linear horizontal) polarized light with the electric field out of (in) the mirror plane (see detailed discussion in Note S3, Supporting Information).…”

Section: Resultssupporting

confidence: 84%

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Topology Hierarchy of Transition Metal Dichalcogenides Built from Quantum Spin Hall Layers

Fang

et al. 2023

Advanced Materials

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The evolution of the physical properties of 2D material from monolayer limit to the bulk reveals unique consequences from dimension confinement and provides a distinct tuning knob for applications. Monolayer 1T'‐phase transition metal dichalcogenides (1T'‐TMDs) with ubiquitous quantum spin Hall (QSH) states are ideal 2D building blocks of various 3D topological phases. However, the stacking geometry has been previously limited to the bulk 1T'‐WTe2 type. Here, the novel 2M‐TMDs consisting of translationally stacked 1T'‐monolayers are introduced as promising material platforms with tunable inverted bandgaps and interlayer coupling. By performing advanced polarization‐dependent angle‐resolved photoemission spectroscopy as well as first‐principles calculations on the electronic structure of 2M‐TMDs, a topology hierarchy is revealed: 2M‐WSe2, MoS2, and MoSe2 are weak topological insulators (WTIs), whereas 2M‐WS2 is a strong topological insulator (STI). Further demonstration of topological phase transitions by tunning interlayer distance indicates that band inversion amplitude and interlayer coupling jointly determine different topological states in 2M‐TMDs. It is proposed that 2M‐TMDs are parent compounds of various exotic phases including topological superconductors and promise great application potentials in quantum electronics due to their flexibility in patterning with 2D materials.

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Section: Resultssupporting

confidence: 85%

\overline Y - \overline \Gamma - \overline Y

(see Figure 4b‐i) and

\overline Y - Z - \overline Y

Section: Resultssupporting

confidence: 84%

Topology Hierarchy of Transition Metal Dichalcogenides Built from Quantum Spin Hall Layers

Fang

et al. 2023

Advanced Materials

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“…The formation of the TSC state in stoichiometric 2M-WS 2 , together with its layered structure with van der Waals coupling, makes it ideal for device fabrication and thus a promising platform to explore the phenomena of MBSs and their application in topological quantum computation. Moreover, the discovery of the TSC state in 2M-WS 2 further enriches the interesting phenomena hosted by TMDs (e.g., gate and pressure-tunable superconductivity 19 , 35 – 39 , charge density waves 38 – 41 , Mott insulators 38 , 39 , gyrotropic electronic orders 42 , moiré-trapped valley excitons 43 , type-II Dirac and Weyl semimetals 44 – 46 , etc. ), thus enabling the study of these properties and their interplay, as well as the design of novel devices for new applications.…”

Section: Discussionmentioning

confidence: 93%

Observation of topological superconductivity in a stoichiometric transition metal dichalcogenide 2M-WS2

Zheng

Fang

et al. 2021

Nat Commun

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Topological superconductors (TSCs) are unconventional superconductors with bulk superconducting gap and in-gap Majorana states on the boundary that may be used as topological qubits for quantum computation. Despite their importance in both fundamental research and applications, natural TSCs are very rare. Here, combining state of the art synchrotron and laser-based angle-resolved photoemission spectroscopy, we investigated a stoichiometric transition metal dichalcogenide (TMD), 2M-WS2 with a superconducting transition temperature of 8.8 K (the highest among all TMDs in the natural form up to date) and observed distinctive topological surface states (TSSs). Furthermore, in the superconducting state, we found that the TSSs acquired a nodeless superconducting gap with similar magnitude as that of the bulk states. These discoveries not only evidence 2M-WS2 as an intrinsic TSC without the need of sensitive composition tuning or sophisticated heterostructures fabrication, but also provide an ideal platform for device applications thanks to its van der Waals layered structure.

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“…[ 39 ] One might notice that only a part of features with similar spectral weight in the calculations have been experimentally resolved, which we attribute to the matrix element effect and a finite photoelectron mean‐free‐path. [ 40 ] The latter factor results in strong spectral weight from the top layer and much weakened signals from the layers below. The pocket centered at K 1,3 , as indicated by the blue arrow in Figure 2c,d, contributes the most significant spectral weight, which originates from the Dirac cone of the top and bottom graphene layers.…”

Section: Resultsmentioning

confidence: 99%

Observation of Coexisting Dirac Bands and Moiré Flat Bands in Magic‐Angle Twisted Trilayer Graphene

Zhang

Fanqiang

et al. 2022

Advanced Materials

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Moiré superlattices that consist of two or more layers of two-dimensional materials stacked together with a small twist angle have emerged as a tunable platform to realize various correlated and topological phases, such as Mott insulators, unconventional superconductivity and quantum anomalous Hall effect. Recently, the magic-angle twisted trilayer graphene (MATTG) has shown both robust superconductivity similar to magic-angle twisted bilayer graphene (MATBG) and other unique properties, including the Pauli-limit violating and re-entrant superconductivity. These rich properties are deeply rooted in its electronic structure under the influence of distinct moiré potential and mirror symmetry. Here, combining nanometer-scale spatially resolved angle-resolved photoemission spectroscopy (nano-ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS), we systematically measure the yet unexplored band structure of MATTG near charge neutrality. Our measurements reveal the coexistence of the distinct dispersive Dirac band with the emergent moiré flat band, showing nice agreement with the theoretical calculations. These results serve as a stepstone for further understanding of the unconventional superconductivity in MATTG.

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Recent Advances in Topological Quantum Materials by Angle-Resolved Photoemission Spectroscopy

Cited by 22 publications

References 151 publications

Topology Hierarchy of Transition Metal Dichalcogenides Built from Quantum Spin Hall Layers

Topology Hierarchy of Transition Metal Dichalcogenides Built from Quantum Spin Hall Layers

Observation of topological superconductivity in a stoichiometric transition metal dichalcogenide 2M-WS2

Observation of Coexisting Dirac Bands and Moiré Flat Bands in Magic‐Angle Twisted Trilayer Graphene

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