Three-Dimensional Real Space Invariants, Obstructed Atomic Insulators and A New Principle for Active Catalytic Sites

Xu, Yuanfeng; Elcoro, Luis; Li, Guowei; Song, Zhida; Regnault, Nicolas; Yang, Qun; Sun, Yan; Parkin, Stuart; Felser, Claudia; Bernevig, B. Andrei

doi:10.48550/arxiv.2111.02433

Cited by 19 publications

(42 citation statements)

References 42 publications

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“…Although the band inversion typically signals to have nontrivial topological nature, both its topological indictor and mirror chern number equal to zero, indicating a topological trivial insulator. Furthermore, by deriving its electronic band structure of the edge boundary, metallic edge states nevertheless occur, which is very similar to the metallic surface states of 3D OAIs 45,46 . Interestingly, we further revealed that in total 16 monolayer MA 2 Z 4 semiconductors with 34 valence electrons (VEC) including experimentally synthesized ilar electronic band features to α 1 -WSn 2 N 4 and they all are topological trivial insulators.…”

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confidence: 79%

“…Recently, a series of unique topologically trivial insulators, dubbed obstructed atomic insulators (OAIs), have been found 45,46 . In difference from the BRs of atomic insulators induced from the atomic orbitals locating at atomoccupied Wyckoff positions (AOWPs), the BRs of OAIs are induced from additional atom-unoccupied Wyckoff positions (AUWPs).…”

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confidence: 99%

“…Importantly, when the cleavage termination cuts through those electron-filled AUWPs (namely, OWCCs) in an OAI, the metallic surface states will emerge. This crucial feature makes OAIs be potential candidates for superconductivity and catalysis [46][47][48][49][50] . To date, OAIs including 3,383 paramagnetic and 30 magnetic materials are reported in threedimensional (3D) materials 45,46 .…”

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confidence: 99%

“…This crucial feature makes OAIs be potential candidates for superconductivity and catalysis [46][47][48][49][50] . To date, OAIs including 3,383 paramagnetic and 30 magnetic materials are reported in threedimensional (3D) materials 45,46 . However, 2D OAIs, which could be used in low dimensional devices 51,52 , have not been systematically investigated.…”

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confidence: 99%

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Two-dimensional Obstructed Atomic Insulators with Fractional Corner Charge in MA$_2$Z$_4$ Family

Wang¹,

Jiang²,

Liu³

et al. 2022

Preprint

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According to topological quantum chemistry, a class of electronic materials have been called obstructed atomic insulators (OAIs), in which a portion of valence electrons necessarily have their centers located on some empty Wyckoff positions without atoms occupation in the lattice. The obstruction of centering these electrons coinciding with their host atoms is nontrivial and results in metallic boundary states when the boundary is properly cut. Here, on basis of first-principles calculations in combination with topological quantum chemistry analysis, we propose two dimensional MA2Z4 (M = Cr, Mo and W; A = Si and Ge, Z = N, P and As) monolayer family are all OAIs. A typical case is the recently synthesized MoSi2N4. Although it is a topological trivial insulator with the occupied electronic states being integer combination of elementary band representations, it has valence electrons centering empty Wyckoff positions. It exhibits unique OAI-induced metallic edge states along the (1 10) edge of MoSi2N4 monolayer and the in-gap corner states at three vertices of certain hexagonal nanodisk samples respecting C3 rotation symmetry. The readily synthesized MoSi2N4 is quite stable and has a large bulk band gap of 1.94 eV, which makes the identification of these edge and corner states most possible for experimental clarification.

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confidence: 79%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Two-dimensional Obstructed Atomic Insulators with Fractional Corner Charge in MA$_2$Z$_4$ Family

Wang¹,

Jiang²,

Liu³

et al. 2022

Preprint

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“…The higher-order topology can be captured by topological quantum chemistry [13][14][15] , nested Wilson loop method 1,8 and second Stiefel-Whitney class [16][17][18][19][20][21][22] . Using topological quantum chemistry 13 , the HOTI can be diagnosed by the decomposition of atomic band representations (aBRs) as an unconventional insulator with mismatching of electronic charge centers and atomic positions 14,15,23 . In contrast to dipoles (Berry phase) for topological insulators, the HOTI can be understood by multipole moments 1 .…”

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confidence: 99%

Quadrupole topological insulators in Ta$_2M_3$Te$_5$ ($M=$ Ni, Pd) monolayers

Guo,

Deng,

Xie

et al. 2022

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Higher-order topological insulators have been introduced in the precursory BBH quadrupole model, but no electronic compound has been proposed to be a quadrupole topological insulator (QTI) yet. In this work, we predict that Ta2M3Te5 (M = Pd, Ni) monolayers can be 2D QTIs with second-order topology due to the double-band inversion. A time-reversal-invariant system with two mirror reflections (Mx and My) can is classified by Stiefel-Whitney (SW) numbers (w1, w2) due to the combined symmetry T C2z. Using the Wilson loop method, we compute w1 = 0 and w2 = 1 for Ta2Ni3Te5, indicating a QTI with q xy = e/2. Thus, gapped edge states and localized corner states are obtained. By analyzing atomic band representations, we demonstrate that its unconventional nature with an essential BR at an empty site, i.e., Ag@4e, is due to the remarkable double-band inversion on Γ-Y. Then, we construct an eight-band quadrupole model with Mx and My successfully for electronic materials. These transition-metal compounds of A2M1,3X5 family provide a good platform for realizing the QTI and exploring the interplay between topological order and interactions.

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Obstructed Surface States as the Descriptor for Predicting Catalytic Active Sites in Inorganic Crystalline Materials

Song

et al. 2022

Advanced Materials

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for the design of highly active catalysts is the identification of the origin of the activity. However, this remains a challenge. [8,9] The activity of a given catalyst is traditionally associated with the properties of its surfaces. Thus, materials with large surface areas, good conductivity, and high mobility are understood to be good catalysts, as they have abundant active sites that favor the adsorption of intermediates and electron transfer in redox reactions. This is the motivation for widely used catalyst synthesis strategies such as nanostructuring, doping, alloying, or adding defects. Each method aims to either expose preferential crystal surfaces or engineer them to make them more active. [10][11][12] However, it is still a formidable task to locate the position of active sites rapidly and precisely from the design perspective, making the discovery of high-performance catalysts from the many potentially interesting materials a challenge.Topological materials have robust surface states and massless electrons with high mobilities. [13][14][15] Moreover, many state-of-the-art catalysts (such as Pt, Pd, Cu, Au, IrO 2 , and RuO 2 ) are understood, either from theory or experiment, to have topologically derived surface states (TSSs). [16,17] Thus, there is some evidence for the important role of TSSs in catalytic reactions. [18,19] Such states are mainly composed of The discovery of new catalysts that are efficient and sustainable is a major research endeavor for many industrial chemical processes. This requires an understanding and determination of the catalytic origins, which remains a challenge. Here, a novel method to identify the position of active sites based on searching for crystalline symmetry-protected obstructed atomic insulators (OAIs) that have metallic surface states is described. The obstructed Wannier charge centers (OWCCs) in OAIs are pinned by symmetries at some empty Wyckoff positions so that surfaces that accommodate these sites are guaranteed to have metallic obstructed surface states (OSSs). It is proposed and confirmed that the OSSs are the catalytic activity origins for crystalline materials. The theory on 2H-MoTe 2 , 1T′-MoTe 2 , and NiPS 3 bulk single crystals is verified, whose active sites are consistent with the calculations. Most importantly, several high-efficiency catalysts are successfully identified just by considering the number of OWCCs and the symmetry. Using the real-spaceinvariant theory applied to a database of 34 013 topologically trivial insulators, 1788 unique OAIs are identified, of which 465 are potential high-performance catalysts. The new methodology will facilitate and accelerate the discovery of new catalysts for a wide range of heterogeneous redox reactions.

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Three-Dimensional Real Space Invariants, Obstructed Atomic Insulators and A New Principle for Active Catalytic Sites

Cited by 19 publications

References 42 publications

Two-dimensional Obstructed Atomic Insulators with Fractional Corner Charge in MA$_2$Z$_4$ Family

Two-dimensional Obstructed Atomic Insulators with Fractional Corner Charge in MA$_2$Z$_4$ Family

Quadrupole topological insulators in Ta$_2M_3$Te$_5$ ($M=$ Ni, Pd) monolayers

Obstructed Surface States as the Descriptor for Predicting Catalytic Active Sites in Inorganic Crystalline Materials

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