Anisotropic optical spectra of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">BaCo</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ni</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">S</mml:mi></mml:mrow><mml:

Takenaka, K.; Kashima, Sae; Osuka, A; Sugai, S.; Yasui, Yukihiko; Shamoto, S.; Sato, M.

doi:10.1103/physrevb.63.115113

Cited by 10 publications

(11 citation statements)

References 41 publications

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“…In any case, the important point here is to remark that the energy of both the AF gap (∼ 40 meV) and the activation energy are much smaller than the proposed energy for a Mott gap in this material (∼ 1 eV) [21]. Even more important, this AF gap is absent above room temperature, where the Mott insulating phase has been claimed.…”

Section: Optical Conductivity Measurementsmentioning

confidence: 66%

Linear behavior of the optical conductivity and incoherent charge transport in BaCoS2

Santos-Cottin

Klein

Werner

et al. 2018

Phys. Rev. Materials

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Optical conductivity measurements on a BaCoS 2 single crystal unveil an unusual linear behavior over a broad spectral range. In the paramagnetic phase above 300 K, the spectrum shows no gap, which contradicts the previously proposed scenario of a charge-transfer Mott insulator. Ab initio dynamical mean field theory calculations including a retarded Hubbard interaction explain the data in terms of an incipient opening of a Co(3d)-S(3p) charge-transfer gap concomitant to incoherent charge transport driven by electronic correlations. These results point to a non-Fermi liquid scenario with Hund's metal properties in the paramagnetic state, which arises from an incipient Mott phase destabilized by low-energy charge fluctuations across the vanishing 3d-3p charge-transfer gap.

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Section: Optical Conductivity Measurementsmentioning

confidence: 66%

Linear behavior of the optical conductivity and incoherent charge transport in BaCoS2

Santos-Cottin

Klein

Werner

et al. 2018

Phys. Rev. Materials

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“…The insulating end member BaCoS 2 displays antiferromagnetic order just above room temperature with a high spin Co 2+ configuration [5]. BaCoS 2 has been reported to be a charge-transfer insulator with strong electron correlations [6,7]. In BaCoS 2 , there is a small monoclinic (P 2/c) distortion to the compound in the plane of the layers, creating two unique bond lengths between the Co and the basal S [3].…”

Section: Introductionmentioning

confidence: 99%

Structural signatures of the insulator-to-metal transition in BaCo1−xNixS2

Schueller

Miller

Zhang

et al. 2020

Phys. Rev. Materials

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The solid solution BaCo1−xNixS2 exhibits an insulator-to-metal transition close to x = 0.21. Questions of whether this transition is coupled with structural changes remain open. Here we follow the structural evolution as a function of the Ni content x using synchrotron powder X-ray diffraction and pair distribution function analyses, to reveal significant basal sulfide anion displacements occurring preferentially along the CoS5 pyramidal edges comprising the edge-connected bond network in BaCo1−xNixS2. These displacements decrease in magnitude as x increases and are nearly quenched in x = 1 BaNiS2. Density functional theory-based electronic structure calculations on x = 0 BaCoS2 suggest that these displacements arise as a dynamic first-order Jahn-Teller effect owing to partial occupancy of nominally degenerate Co 2+ dxz and dyz orbitals, leading to local structural symmetry breaking in the xy-plane of the Co-rich phases. The Jahn-Teller instability is associated with opening of a band gap that is further strengthened by electronic correlation. The Jahn-Teller effect is reduced upon increased electron filling as x → 1, indicating local structure and band filling cooperatively result in the observed insulator-to-metal transition.

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“…However, the ARPES result does not show any indi- cation of the band-folding, which may be related to the weak exchange coupling Jϭ7 -8 meV reported recently by Raman scattering. 18 Further, the energy scale dominating the MIT ͑order of 0.1 eV as found in Fig. 3͒ seems much larger than J in contrast with the case of the high-T c cuprate (Sr 2 CuO 2 Cl 2 ) 2 , where the observed band width (ϳ0.3 eV) is comparable to the exchange energy (2.2J), but far smaller than the prediction from the band calculation.…”

mentioning

confidence: 54%

“…Next, we discuss the origin for the insulating nature of BaCo 1Ϫx Ni x S 2 at xϭ0. 18. The structural distortion observed in BaCoS 2 6 seems unlikely since the lattice instability due to the monoclinic distortion is quickly suppressed with Ni substitution and is no longer present at xϾ0.1.…”

mentioning

confidence: 96%

“…On the other hand, considering the relatively narrow band width near E F in BaCo 0.82 Ni 0.18 S 2 compared with the band calculation, it is inferred that the electron correlation among d electrons has still an essential role in characterizing the insulating nature at xϭ0. 18, and the MIT may be understood in terms of the successive change in the effective cor-relation energy with Ni substitution.…”

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confidence: 99%

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Evolution of metallic states from the Hubbard band in the two-dimensional Mott systemBaCo1−xNix

et al. 2001

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We report angle-resolved photoemission spectroscopy on the layered Mott system BaCo 1Ϫx Ni x S 2. ͑x ϭ0.18, 0.28͒ across the phase transition from the antiferromagnetic insulator to anomalous metal. We found that the lower Hubbard band in the insulating phase possesses a remnant of the Fermi surface in the metallic phase and gradually evolves into the metallic bands with carrier doping. We compare the experimental result with those of the high-T c cuprates to discuss the absence of superconductivity in BaCo 1Ϫx Ni x S 2 .

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Anisotropic optical spectra ofBaCo1−xNixS

Cited by 10 publications

References 41 publications

Linear behavior of the optical conductivity and incoherent charge transport in BaCoS2

Linear behavior of the optical conductivity and incoherent charge transport in BaCoS2

Structural signatures of the insulator-to-metal transition in BaCo1−xNixS2

Evolution of metallic states from the Hubbard band in the two-dimensional Mott systemBaCo1−xNix

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