Spin fluctuations, magnetic long-range order, and Fermi surface gapping in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Na</mml:mtext></mml:mrow><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mrow><mml:mtext>CoO</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Schulze, T. F.; Brühwiler, M.; Häfliger, P. S.; Казаков, С. М.; Niedermayer, Ch.; Mattenberger, K.; Karpiński, J.; Batlogg, B.

doi:10.1103/physrevb.78.205101

Cited by 14 publications

(9 citation statements)

References 41 publications

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“…The case x=0.5 seems exceptional, with in-plane AFM order 21 in the insulating regime. For x>0.5 the system displays increasing magnetical response with a spin-fluctuation regime in the range 0.6<x<3/4, including the evolution to Curie-Weiss behavior 13 for 0.6<x<0.67, and the eventual onset of in-plane ferromagnetic (FM) order 15,[22][23][24][25][26][27][28][29][30] . The magnetic structure in the doping range 3/4<x<0.9 with ordering temperatures T N ∼19-27K [21][22][23][24]27 is of Atype, i.e., the FM CoO 2 layers are coupled antiferromagnetically.…”

Section: Introductionmentioning

confidence: 99%

Considerable nonlocal electronic correlations in strongly dopedNaxCoO2

Piefke¹,

Boehnke²,

Georges³

et al. 2010

Phys. Rev. B

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The puzzling electronic correlation effects in the sodium cobaltate system are studied by means of the combination of density functional theory and the rotationally invariant slave boson (RISB) method in a cellular-cluster approach. Realistic non-local correlations are hence described in the short-range regime for finite Coulomb interactions on the underlying frustrated triangular lattice. A local Hubbard U is sufficient to model the gross in-plane magnetic behavior with doping x, namely antiferromagnetic correlations at intermediate doping and the onset of ferromagnetic order above x>3/4 with a mixed phase for 0.62

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Section: Introductionmentioning

confidence: 99%

Considerable nonlocal electronic correlations in strongly dopedNaxCoO2

Piefke¹,

Boehnke²,

Georges³

et al. 2010

Phys. Rev. B

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“…Remarkably, most of the signatures of strong correlations in cobaltates, such as specific-heat enhancement [8], band narrowing [7,[9][10][11] or strong electron-electron scattering [12] are observed in the high-doping region x ∈ [1/2, 1] close to the band-insulating limit (x = 1). Besides intriguing magnetic behavior, charge disproportionation is a prominent feature in this part of the phase diagram.…”

mentioning

confidence: 99%

Strong Correlations Enhanced by Charge Ordering in Highly Doped Cobaltates

2011

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We present an explanation for the puzzling spectral and transport properties of layered cobaltates close to the band-insulator limit, which relies on the key effect of charge ordering. Blocking a significant fraction of the lattice sites deeply modifies the electronic structure in a way that is shown to be quantitatively consistent with photoemission experiments. It also makes the system highly sensitive to interactions (especially to intersite ones), hence accounting for the strong correlations effects observed in this regime, such as the high effective mass and quasiparticle scattering rate. These conclusions are supported by a theoretical study of an extended Hubbard model with a realistic band structure on an effective kagomé lattice.The layered cobaltate metals are famous for their remarkable electronic properties [1], ranging from a large thermoelectric response [2] charge-ordering [3,4] and puzzling magnetic behavior, to superconductivity when intercalated with water [5]. Because of the universality of the physical properties throughout the cobaltate family, it is believed that most of these properties have their roots in the electronic structure of the CoO 2 layers. Those are formed of edge-sharing octahedra, with the Co ions forming a triangular lattice. Either alkali(-earth) metals (Na, Li, Ca etc., as in Na x CoO 2 ) or more complex building blocks (e.g. rocksalt BiO or SrO planes in misfit cobaltates [6]) separate the layers and serve as electron donors. Varying the composition of the intercalated compounds controls the doping x ∈ [0, 1], resulting in a nominal Co (4−x)+ (3d 5+x ) valence in the low-spin configuration within the t 2g manifold. The latter is split by the local trigonal symmetry into one a 1g and two e g states. Strong Coulomb interactions have been documented [7] to occur within this orbital subspace.

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“…12 More specifically, the latter compound belongs to a family of doped Mott insulators [13][14][15] which has revealed striking properties [16][17][18] such as an enhanced room-temperature thermopower 19,20 and a large negative magnetoresistance. 21 Interestingly, the so-called giant electron-electron scattering inferred in Na 0.7 CoO 2 22 has already led to conjecture of a possible influence of a magnetic QCP in qualitative agreement with density functional calculations predicting a weak itinerant ferromagnetic state competing with a weak itinerant antiferromagnetic state.…”

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confidence: 99%

ω/Tscaling of the optical conductivity in strongly correlated layered cobalt oxide

et al. 2013

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We report infrared spectroscopic properties of the strongly correlated layered cobalt oxide [BiBa0.66K0.36O2]CoO2. These measurements performed on single crystals allow us to determine the optical conductivity as a function of temperature. In addition to a large temperature dependent transfer of spectral weight, an unconventional low energy mode is found. We show that both its frequency and damping scale as the temperature itself. In fact, a basic analysis demonstrates that this mode fully scales onto a function of ω/T up to room temperature. This behavior suggests low energy excitations of non-Fermi liquid type originating from quantum criticality.

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Spin fluctuations, magnetic long-range order, and Fermi surface gapping inNaxCoO2

Cited by 14 publications

References 41 publications

Considerable nonlocal electronic correlations in strongly dopedNaxCoO2

Considerable nonlocal electronic correlations in strongly dopedNaxCoO2

Strong Correlations Enhanced by Charge Ordering in Highly Doped Cobaltates

ω/Tscaling of the optical conductivity in strongly correlated layered cobalt oxide

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