scholarly journals Chern insulator with a nearly flat band in the metal-organic-framework-based Kagome lattice

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Santu Baidya ◽  
Seungjin Kang ◽  
Choong H. Kim ◽  
Jaejun Yu
Keyword(s):  
Density Functional ◽  
Metal Organic Framework ◽  
Chern Number ◽  
Flat Band ◽  
Kagome Lattice ◽  
Kagomé Lattice ◽  
Topological Quantum ◽  
Metal Organic ◽  
Fe Complexes ◽  
Carrier Doping

Abstract Based on first-principles density-functional theory (DFT) calculations, we report that the transition-metal bis-dithiolene, M3C12S12 (M = Mn and Fe), complexes can be a two-dimensional (2D) ferromagnetic insulator with nontrivial Chern number. Among various synthetic pathways leading to metal bis-dithiolenes, the simplest choice of ligand, Benzene-hexathiol, connecting metal cations to form a Kagome lattice is studied following the experimental report of time-reversal symmetric isostructural compound Ni3C12S12. We show sulfur and carbon-based ligands play the key role in making the complexes topologically nontrivial. An unusual topological quantum phase transition induced by the on-site Coulomb interaction brings a nearly flat band with a nonzero Chern number as the highest occupied band. With this analysis we explain the electronic structure of the class M3C12S12 and predict the existence of nearly flat band with nonzero Chern number and it can be a fractional Chern insulator candidate with carrier doping.

scholarly journals A density-wave-like transition in the polycrystalline V3Sb2 sample with bilayer kagome lattice

2021 ◽  
Author(s):  
N. N. Wang ◽  
Y. H. Gu ◽  
M. A. McGuire ◽  
J. Q. Yan ◽  
L. F. Shi ◽  
...  
Keyword(s):  
Density Functional ◽  
Thermal Hysteresis ◽  
Density Wave ◽  
Density Functional Theory Calculations ◽  
Solid State Reaction Method ◽  
Kagome Lattice ◽  
Conventional Solid State Reaction ◽  
Kagomé Lattice ◽  
Preparation Conditions ◽  
Topological Quantum

Abstract Recently, transition-metal-based kagome metals have aroused much research interest as a novel platform to explore exotic topological quantum phenomena. Here we report on the synthesis, structure, and physical properties of a bilayer kagome lattice compound V3Sb2. The polycrystalline V3Sb2 samples were synthesized by conventional solid-state-reaction method in a sealed quartz tube at temperatures below 850 ℃. Measurements of magnetic susceptibility and resistivity revealed consistently a density-wave-like transition at T dw ≈ 160 K with a large thermal hysteresis, even though some sample-dependent behaviors are observed presumably due to the different preparation conditions. Upon cooling through T dw, no strong anomaly in lattice parameters and no indication of symmetry lowering were detected in powder x-ray diffraction measurements. This transition can be suppressed completely by applying hydrostatic pressures of about 1.8 GPa, around which no sign of superconductivity is observed down to 1.5 K. Specific-heat measurements reveal a relatively large Sommerfeld coefficient γ = 18.5 mJ/mol-K2, confirming the metallic ground state with moderate electronic correlations. Density functional theory calculations indicate that V3Sb2 shows a non-trivial topological crystalline property. Thus, our study makes V3Sb2 a new candidate of metallic kagome compound to study the interplay between density-wave-order, nontrivial band topology, and possible superconductivity.

scholarly journals First-principles design of a half-filled flat band of the kagome lattice in two-dimensional metal-organic frameworks

2016 ◽  
Vol 94 (8) ◽  
Author(s):  
Masahiko G. Yamada ◽  
Tomohiro Soejima ◽  
Naoto Tsuji ◽  
Daisuke Hirai ◽  
Mircea Dincă ◽  
...  
Keyword(s):  
First Principles ◽  
Metal Organic Frameworks ◽  
Flat Band ◽  
Two Dimensional ◽  
Kagome Lattice ◽  
Kagomé Lattice ◽  
Metal Organic

scholarly journals Strongly correlated superconductivity in a copper-based metal-organic framework with a perfect kagome lattice

2021 ◽  
Vol 7 (12) ◽  
pp. eabf3996
Author(s):  
T. Takenaka ◽  
K. Ishihara ◽  
M. Roppongi ◽  
Y. Miao ◽  
Y. Mizukami ◽  
...  
Keyword(s):  
Metal Organic Framework ◽  
Superfluid Density ◽  
Quantum Spin ◽  
Spin Fluctuations ◽  
Strongly Correlated ◽  
Spin Liquids ◽  
Kagome Lattice ◽  
Unconventional Superconductor ◽  
Kagomé Lattice ◽  
Metal Organic

Metal-organic frameworks (MOFs), which are self-assemblies of metal ions and organic ligands, provide a tunable platform to search a new state of matter. A two-dimensional (2D) perfect kagome lattice, whose geometrical frustration is a key to realizing quantum spin liquids, has been formed in the π − d conjugated 2D MOF [Cu3(C6S6)]n (Cu-BHT). The recent discovery of its superconductivity with a critical temperature Tc of 0.25 kelvin raises fundamental questions about the nature of electron pairing. Here, we show that Cu-BHT is a strongly correlated unconventional superconductor with extremely low superfluid density. A nonexponential temperature dependence of superfluid density is observed, indicating the possible presence of superconducting gap nodes. The magnitude of superfluid density is much smaller than those in conventional superconductors and follows the Uemura’s relation of strongly correlated superconductors. These results imply that the unconventional superconductivity in Cu-BHT originates from electron correlations related to spin fluctuations of kagome lattice.

scholarly journals Selective capture of carbon dioxide from hydrocarbons using a metal-organic framework

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Omid T. Qazvini ◽  
Ravichandar Babarao ◽  
Shane G. Telfer
Keyword(s):  
Carbon Dioxide ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Time Lags ◽  
X Ray Crystallography ◽  
Metal Organic ◽  
Adsorption Of Co ◽  
Short Time ◽  
Organic Framework

AbstractEfficient and sustainable methods for carbon dioxide capture are highly sought after. Mature technologies involve chemical reactions that absorb CO2, but they have many drawbacks. Energy-efficient alternatives may be realised by porous physisorbents with void spaces that are complementary in size and electrostatic potential to molecular CO2. Here, we present a robust, recyclable and inexpensive adsorbent termed MUF-16. This metal-organic framework captures CO2 with a high affinity in its one-dimensional channels, as determined by adsorption isotherms, X-ray crystallography and density-functional theory calculations. Its low affinity for other competing gases delivers high selectivity for the adsorption of CO2 over methane, acetylene, ethylene, ethane, propylene and propane. For equimolar mixtures of CO2/CH4 and CO2/C2H2, the selectivity is 6690 and 510, respectively. Breakthrough gas separations under dynamic conditions benefit from short time lags in the elution of the weakly-adsorbed component to deliver high-purity hydrocarbon products, including pure methane and acetylene.

scholarly journals Flat-Band-Enabled Triplet Excitonic Insulator in a Diatomic Kagome Lattice

2021 ◽  
Vol 126 (19) ◽  
Author(s):  
Gurjyot Sethi ◽  
Yinong Zhou ◽  
Linghan Zhu ◽  
Li Yang ◽  
Feng Liu
Keyword(s):  
Flat Band ◽  
Kagome Lattice ◽  
Kagomé Lattice ◽  
Excitonic Insulator

scholarly journals Exposing unsaturated Cu1-O2 sites in nanoscale Cu-MOF for efficient electrocatalytic hydrogen evolution

2021 ◽  
Vol 7 (18) ◽  
pp. eabg2580
Author(s):  
Weiren Cheng ◽  
Huabin Zhang ◽  
Deyan Luan ◽  
Xiong Wen (David) Lou
Keyword(s):  
Hydrogen Evolution ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Active Centers ◽  
Functional Theory ◽  
Hollow Nanostructure ◽  
Metal Organic ◽  
X Ray Absorption ◽  
A Current

Conductive metal-organic framework (MOF) materials have been recently considered as effective electrocatalysts. However, they usually suffer from two major drawbacks, poor electrochemical stability and low electrocatalytic activity in bulk form. Here, we have developed a rational strategy to fabricate a promising electrocatalyst composed of a nanoscale conductive copper-based MOF (Cu-MOF) layer fully supported over synergetic iron hydr(oxy)oxide [Fe(OH)x] nanoboxes. Owing to the highly exposed active centers, enhanced charge transfer, and robust hollow nanostructure, the obtained Fe(OH)x@Cu-MOF nanoboxes exhibit superior activity and stability for the electrocatalytic hydrogen evolution reaction (HER). Specifically, it needs an overpotential of 112 mV to reach a current density of 10 mA cm−2 with a small Tafel slope of 76 mV dec−1. X-ray absorption fine structure spectroscopy combined with density functional theory calculations unravels that the highly exposed coordinatively unsaturated Cu1-O2 centers could effectively accelerate the formation of key *H intermediates toward fast HER kinetics.

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