Prediction of large gap flat Chern band in a two-dimensional metal-organic framework

Su, Ninghai; Jiang, Wei; Wang, Zhengfei; Liu, Feng

doi:10.1063/1.5017956

Cited by 44 publications

(33 citation statements)

References 36 publications

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“…The topological nodal line is not protected by any crystal symmetry, and is gapped by including SOC to become a strong 3D topological metal, as confirmed by both Z 2 index and topological surface state calculations. Our results demonstrate the possibility of controllably generating 3D topological states by pressure, and pave the way for searching and designing topological states in 3D organometallic materials [21][22][23][24][25][26] by strain engineering.…”

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confidence: 63%

Pressure-induced organic topological nodal-line semimetal in the three-dimensional molecular crystal Pd(dddt)2

Liu

Wang

et al. 2018

Phys. Rev. B

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The nodal-line semimetal represents a new class of topological materials characterized with highest band degeneracy. It is usually found in inorganic materials of high crystal symmetry or a minimum symmetry of inversion aided with accidental band degeneracy [Phys. Rev. Lett. 118, 176402 (2017)]. Based on first-principles band structure, Wannier charge center and topological surface state calculations, here we predict a pressure-induced topological nodal-line semimetal in the absence of spin-orbit coupling (SOC) in the newly synthesized single-component 3D molecular crystal Pd(dddt)2. We show a Γ-centered single nodal line undulating within a narrow energy window across the Fermi level. This intriguing nodal line is generated by pressure-induced accidental band degeneracy, without protection from any crystal symmetry. When SOC is included, the fourfold degenerated nodal line is gapped and Pd(dddt)2 becomes a strong 3D topological metal with an Z2 index of (1;000). However, the tiny SOC gap makes it still possible to detect the nodal-line properties experimentally. Our findings afford an attractive route for designing and realizing topological states in 3D molecular crystals, as they are weakly bonded through Van der Waals forces with a low crystal symmetry so that their electronic structures can be easily tuned by pressure.

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confidence: 63%

Pressure-induced organic topological nodal-line semimetal in the three-dimensional molecular crystal Pd(dddt)2

Liu

Wang

et al. 2018

Phys. Rev. B

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“…We note that hopping terms can also be tuned by a chain of waveguide 20,49 , which could possibly be used to tune the band dispersion to realize the transition between type-I and type-II Dirac states. On the other hand, the Lieb and Kagome lattices have been separately proposed in real material systems, such as the 2D metal-organic and covelent-organic frameworks (MOF/COF) 24,[50][51][52][53] . Considering the high tunability of the MOF/COFs 54,55 , it is also possible to find suitable real 2D material systems to realize such phase transition.…”

Section: Photonic Waveguide Systemmentioning

confidence: 99%

Topological band evolution between Lieb and kagome lattices

et al. 2019

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Among two-dimensional lattices, both Kagome and Lieb lattices have been extensively studied, showing unique physics related to their exotic flat and Dirac bands. Interestingly, we realize that the two lattices are in fact interconvertible by applying strains along the diagonal direction, as they share the same structural configuration in the unit cell, i.e., one corner-site and two edge-center states. We study phase transitions between the two lattices using the tight-binding approach and propose one experimental realization of the transitions using photonic devices. The evolution of the band structure demonstrates a continuous evolution of the flat band from the middle of the Lieb band to the top/bottom of the Kagome band. Though the flat band is destroyed during the transition, the topological features are conserved due to the retained inversion symmetry, as confirmed by Berry curvature, Wannier charge center, and edge state calculations. Meanwhile, the triply degenerate Dirac point (M ) in the Lieb lattice transforms into two doubly degenerate Dirac points with one of which moves along M -Γ and the other moves along M -K/K directions that form the Kagome band eventually. Interestingly, the Dirac cones in the transition states are strongly tilted, showing a coexistence of type-I and type-II Dirac points. We finally show that these transitions can be experimentally realized in photonic lattices using waveguide arrays.

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“…Although the existence of such states has already been confirmed for limited numbers of inorganic compounds and artificial metamaterials, no experimental data exists for organic, and especially, metal–organic materials. In this case, the calculation approach also helped to reveal that MOF structures satisfy the requisite topological concept (Figure b); since 2013, there have been several theoretical works based on 2D structures confirming the existence of topological states allowing an opposite transfer of electrons with opposite spins . These states should originate from electrons filling the hybridized bands of metal ions and molecular orbitals of the ligands .…”

Section: Transfer Effects In Mofsmentioning

confidence: 88%

“…[65] Although the existence of such states has already been confirmed for limited numbers of inorganic compounds and artificial metamaterials, [66] no experimental data exists for organic, and especially, metal-organic materials. [67][68][69][70][71] These states should originate from electrons filling the hybridized bands of metal ions and molecular orbitals of the ligands. [67][68][69][70][71] These states should originate from electrons filling the hybridized bands of metal ions and molecular orbitals of the ligands.…”

Section: Topological Insulatorsmentioning

confidence: 99%

Metal–Organic Frameworks in Modern Physics: Highlights and Perspectives

et al. 2019

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Owing to the synergistic combination of a hybrid organic–inorganic nature and a chemically active porous structure, metal–organic frameworks have emerged as a new class of crystalline materials. The current trend in the chemical industry is to utilize such crystals as flexible hosting elements for applications as diverse as gas and energy storage, filtration, catalysis, and sensing. From the physical point of view, metal–organic frameworks are considered molecular crystals with hierarchical structures providing the structure‐related physical properties crucial for future applications of energy transfer, data processing and storage, high‐energy physics, and light manipulation. Here, the perspectives of metal–organic frameworks as a new family of functional materials in modern physics are discussed: from porous metals and superconductors, topological insulators, and classical and quantum memory elements, to optical superstructures, materials for particle physics, and even molecular scale mechanical metamaterials. Based on complementary properties of crystallinity, softness, organic–inorganic nature, and complex hierarchy, a description of how such artificial materials have extended their impact on applied physics to become the mainstream in material science is offered.

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Prediction of large gap flat Chern band in a two-dimensional metal-organic framework

Cited by 44 publications

References 36 publications

Pressure-induced organic topological nodal-line semimetal in the three-dimensional molecular crystal Pd(dddt)2

Pressure-induced organic topological nodal-line semimetal in the three-dimensional molecular crystal Pd(dddt)2

Topological band evolution between Lieb and kagome lattices

Metal–Organic Frameworks in Modern Physics: Highlights and Perspectives

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