Signatures for half-metallicity and nontrivial surface states in the kagome lattice Weyl semimetal 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Co</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Sn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">S</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Jiao, Lin; Xu, Qiunan; Cheon, Yeryun; Sun, Yan; Felser, Claudia; Liu, Enke; Wirth, S.

doi:10.1103/physrevb.99.245158

Cited by 53 publications

(66 citation statements)

References 48 publications

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“…1d)the flat dispersion is realized along all three momentum directions in CoSn. This is indeed at variance with the limited momentum range of the flat bands in previously studied kagome compounds [21][22][23][24] . Accordingly, the kinetic energy of flat band electrons in CoSn is strongly quenched, and interaction-driven many-body ground states are naturally expected once this latticeborn flat band is tuned to the Fermi level.…”

Section: Resultssupporting

confidence: 71%

Topological flat bands in frustrated kagome lattice CoSn

et al. 2020

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Electronic flat bands in momentum space, arising from strong localization of electrons in real space, are an ideal stage to realize strongly-correlated phenomena. Theoretically, the flat bands can naturally arise in certain geometrically frustrated lattices, often with nontrivial topology if combined with spin-orbit coupling. Here, we report the observation of topological flat bands in frustrated kagome metal CoSn, using angle-resolved photoemission spectroscopy and band structure calculations. Throughout the entire Brillouin zone, the bandwidth of the flat band is suppressed by an order of magnitude compared to the Dirac bands originating from the same orbitals. The frustration-driven nature of the flat band is directly confirmed by the chiral d-orbital texture of the corresponding real-space Wannier functions. Spin-orbit coupling opens a large gap of 80 meV at the quadratic touching point between the Dirac and flat bands, endowing a nonzero Z 2 invariant to the flat band. These findings demonstrate that kagome-derived flat bands are a promising platform for novel emergent phases of matter at the confluence of strong correlation and topology.

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Section: Resultssupporting

confidence: 71%

Topological flat bands in frustrated kagome lattice CoSn

et al. 2020

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“…Cleaving preferentially breaks its S-Sn bond, which leads to the S and Sn terminated surfaces. Previous STM studies have dominantly observed two surfaces, one with largely vacancy defects and the other with adatom defects 11,13,14 . Several factors challenge their assignation, as the two surfaces have identical lattice symmetries, their interlayer distance is sub-Å in scale, and STM topographic image convolutes the spatial variation of the integrated local density of states and the geometrical corrugations 23 .…”

Section: Resultsmentioning

confidence: 99%

Spin-orbit quantum impurity in a topological magnet

et al. 2020

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Quantum states induced by single-atomic impurities are at the frontier of physics and material science. While such states have been reported in high-temperature superconductors and dilute magnetic semiconductors, they are unexplored in topological magnets which can feature spin-orbit tunability. Here we use spin-polarized scanning tunneling microscopy/ spectroscopy (STM/S) to study the engineered quantum impurity in a topological magnet Co 3 Sn 2 S 2. We find that each substituted In impurity introduces a striking localized bound state. Our systematic magnetization-polarized probe reveals that this bound state is spindown polarized, in lock with a negative orbital magnetization. Moreover, the magnetic bound states of neighboring impurities interact to form quantized orbitals, exhibiting an intriguing spin-orbit splitting, analogous to the splitting of the topological fermion line. Our work collectively demonstrates the strong spin-orbit effect of the single-atomic impurity at the quantum level, suggesting that a nonmagnetic impurity can introduce spin-orbit coupled magnetic resonance in topological magnets.

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“…Furthermore, single-particle ab initio calculations suggest that FM Co 3 Sn 2 S 2 is a contender for magnetic WSMs [50][51][52] . Up to now, important progresses in the experimental studies of the predicted WSM state in FM Co 3 Sn 2 S 2 , which involve the measurements of negative magnetoresistance, giant intrinsic anomalous Hall, Nernst effects, bulk Weyl cones, and surface Fermi arcs 50,52,[58][59][60][61][62][63][64][65] , have been achieved. However, the influence of electronic correlations on the single-particle-abinitio-calculation-derived WSM state in this WSM candidate, for example, inducing a flat band, remains elusive.…”

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confidence: 99%

Electronic correlations and flattened band in magnetic Weyl semimetal candidate Co3Sn2S2

Zhao

et al. 2020

Nat Commun

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The interplay between electronic correlations and topological protection may offer a rich avenue for discovering emergent quantum phenomena in condensed matter. However, electronic correlations have so far been little investigated in Weyl semimetals (WSMs) by experiments. Here, we report a combined optical spectroscopy and theoretical calculation study on the strength and effect of electronic correlations in a magnet Co 3 Sn 2 S 2. The electronic kinetic energy estimated from our optical data is about half of that obtained from single-particle ab initio calculations in the ferromagnetic ground state, which indicates intermediate-strength electronic correlations in this system. Furthermore, comparing the energy and side-slope ratios between the interband-transition peaks at high energies in the experimental and single-particle-calculation-derived optical conductivity spectra with the bandwidth-renormalization factors obtained by many-body calculations enables us to estimate the Coulomb-interaction strength (U ∼ 4 eV) in Co 3 Sn 2 S 2. Besides, a sharp experimental optical conductivity peak at low energy, which is absent in the single-particlecalculation-derived spectrum but is consistent with the optical conductivity peaks obtained by many-body calculations with U ∼ 4 eV, indicates that an electronic band connecting the two Weyl cones is flattened by electronic correlations and emerges near the Fermi energy in Co 3 Sn 2 S 2. Our work paves the way for exploring flat-band-generated quantum phenomena in WSMs.

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Signatures for half-metallicity and nontrivial surface states in the kagome lattice Weyl semimetal Co3Sn2S2

Cited by 53 publications

References 48 publications

Topological flat bands in frustrated kagome lattice CoSn

Topological flat bands in frustrated kagome lattice CoSn

Spin-orbit quantum impurity in a topological magnet

Electronic correlations and flattened band in magnetic Weyl semimetal candidate Co3Sn2S2

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