Considerable nonlocal electronic correlations in strongly doped<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>

Piefke, Christoph; Boehnke, Lewin; Georges, Antoine; Lechermann, Frank

doi:10.1103/physrevb.82.165118

Cited by 12 publications

(15 citation statements)

References 97 publications

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“…While Γ and A show CW behavior, the extrapolated transition temperature however is ∼7% higher at A than at Γ, verifying the experimental findings of A-type order [7][8][9][10]. In the temperature scan we additionally introduced a nearestlayer inter-plane hopping t ⊥ =13 meV [9,13,38], however the previous in-plane results are qualitatively not affected by this model extension. Due to known charge disproportionation the inclusion of long-range Coulomb interactions, e.g., via an inter-site V [13,16], seems reasonable.…”

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confidence: 75%

“…The ordered magnetic structure in the doping range 0.75<x<0.9 with T N ∼19-27K [7][8][9][10] is of A-type AFM for the FM CoO 2 layers. As the local spin-density approximation (LSDA) is not sufficient to account for the AFM-to-FM crossover with x [3], explicit many-body approaches are needed [11][12][13].…”

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confidence: 99%

“…In the temperature scan we additionally introduced a nearestlayer inter-plane hopping t ⊥ =13 meV [9,13,38], however the previous in-plane results are qualitatively not affected by this model extension. Due to known charge disproportionation the inclusion of long-range Coulomb interactions, e.g., via an inter-site V [13,16], seems reasonable. This was abandoned in the present single-site DMFT approach, resulting generally in reduced charge response.…”

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confidence: 99%

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Competing orders in NaxCoO2from strong correlations on a two-particle level

Boehnke

Lechermann

2012

Phys. Rev. B

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Based on dynamical mean-field theory with a continuous-time quantum Monte-Carlo impurity solver, static as well as dynamic spin and charge susceptibilites for the phase diagram of the sodium cobaltate system NaxCoO2 are discussed. The approach includes important vertex contributions to the q-dependent two-particle response functions by means of a local approximation to the irreducible vertex function in the particle-hole channel. A single-band Hubbard model suffices to reveal several charge-and spin-instability tendencies in accordance with experiment, including the stabilization of an effective kagomé sublattice close to x=0.67, without invoking the doping-dependent Na-potential landscape. The in-plane antiferromagnetic-to-ferromagnetic crossover is additionally verified by means of the computed Korringa ratio. Moreover an intricate high-energy mode in the transverse spin susceptiblity is revealed, pointing towards a strong energy dependence of the effective intersite exchange.PACS numbers: 71.27.+a, 71.30.+h, 71.10.Fd, 75.30.Cr The investigation of finite-temperature phase diagrams of realistic strongly correlated systems is a quite formidable task due to the often tight competition between various low-energy ordering instabilities. In this respect the quasi-twodimensional (2D) sodium cobaltate system Na x CoO 2 serves as a notably challenging case [1,2]. Here x∈[0,1] nominally mediates between the Co 4+ (3d 5 , S=1/2) and Co 3+ (3d 6 , S=0) low-spin states. Thus the Na ions provide the electron doping for the nearly filled t 2g states of the triangular CoO 2 layers up to the band-insulating limit x=1. Coulomb correlations with a Hubbard U up to 5 eV for the t 2g manifold of bandwidth W ∼1.5 eV [3] are revealed from photoemission [4]. Hence with U /W 1 the frustrated metallic system is definitely placed in the strongly correlated regime.Various different electronic phases and regions for temperature T vs. doping x are displayed in the experimental sodium cobaltate phase diagram (see Fig. 1). For instance a superconducting dome (T c ∼4.5K) stabilized by intercalation with water close to x=0. Several theoretical works have dealt with the influence of the sodium arrangements on the electronic properties of Na x CoO 2 , both from the viewpoint of disordered sodium ions [12] as well as from orderings for certain dopings. [14][15][16] However, wether such sodium patterns are due to sole (effective) single-particle potentials or mainly originating from many-body effects within the CoO 2 planes is still a matter of debate [17,18].In this letter, we report the fact that a large part of the electronic (spin and charge) phase diagram of sodium cobaltate may be well described within a Hubbard model using realistic dispersions, and without invoking the details of the sodium arrangement. Thereby most of the observed crossovers and instabilities are truly driven by strong correlation effects and cannot be described within weak-coupling scenarios. The theoretical study is elucidating the two-particle correlations in the pa...

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Competing orders in NaxCoO2from strong correlations on a two-particle level

Boehnke

Lechermann

2012

Phys. Rev. B

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“…Note that previous works already showed the importance of nonlocal correlations [32,33]. From a 'molecular orbitals' viewpoint, the CDW transition is driven by orbital polarization: the intersite interaction drives the symmetric orbital |u towards half-filling (hence suscep- tible to a MIT), while the two asymmetric orbitals |d 1,2 are completely filled (with in total 5 = 3(1 + y) electrons in each EKL unit cell).…”

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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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“…Unconventional superconductivity generally emerges in frustrated systems [49][50][51][52][53] when long-range order in the spin, charge or orbital channel is suppressed. The key ingredients needed for a typical unconventional superconductor, strong short-range correlations in these channels, are either negligible or dilute in PdTe.…”

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First-principles Wannier function analysis of the electronic structure of PdTe: weaker magnetism and superconductivity

Ekuma¹,

Lin²,

Moreno³

et al. 2013

J. Phys.: Condens. Matter

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We report a first-principles Wannier function study of the electronic structure of PdTe. Its electronic structure is found to be a broad three-dimensional Fermi surface with highly reduced correlations effects. In addition, the higher filling of the Pd d-shell, its stronger covalency resulting from the closer energy of the Pd-d and Te-p shells, and the larger crystal field effects of the Pd ion due to its near octahedral coordination all serve to weaken significantly electronic correlations in the particle-hole (spin, charge, and orbital) channel. In comparison to the Fe Chalcogenide e.g., FeSe, we highlight the essential features (quasi-two-dimensionality, proximity to half-filling, weaker covalency, and higher orbital degeneracy) of Fe-based high-temperature superconductors.PACS numbers: 31.15. 74.70.Ad, 71.15.Ap, 71.27.+a

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Considerable nonlocal electronic correlations in strongly dopedNaxCoO2

Cited by 12 publications

References 97 publications

Competing orders in NaxCoO2from strong correlations on a two-particle level

Competing orders in NaxCoO2from strong correlations on a two-particle level

Strong Correlations Enhanced by Charge Ordering in Highly Doped Cobaltates

First-principles Wannier function analysis of the electronic structure of PdTe: weaker magnetism and superconductivity

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