Dynamical Mean Field Theory of an Effective Three-Band Model for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Na</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>CoO</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

Bourgeois, A.; Aligia, A. A.; Rozenberg, M. J.

doi:10.1103/physrevlett.102.066402

Cited by 21 publications

(50 citation statements)

References 35 publications

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“…(1)] for the description of the electronic structure of Na x CoO 2 and only positive values (in contrast to the negative ones obtained from LDA) seem consistent with ARPES data. 12,13,15 We obtain ≈ 130 meV. While changes of the order of 1 eV in charge-transfer energy or F 0 (which controls the part of the Coulomb repulsion that does not depend of the symmetry of the orbitals) do not affect very much, we find that is very sensitive to the parameter F 2 , which controls (among others) interaction constants related with the Hund rules (exchange interactions and decrease of interorbital repulsions with respect to intraorbital ones).…”

Section: Summary and Discussionmentioning

confidence: 85%

“…With these parameters and realistic values of the Coulomb repulsion U eff , correlations are not able to reconcile theory with experiment, as shown by different dynamicalmean-field-theory (DMFT) studies. 12,13,15 The pockets still remain in the calculations.…”

Section: Introductionmentioning

confidence: 99%

“…15 In this procedure, no LDA results were used. The parameters of H mb were taken from previous fits of of polarized x-ray absorption spectra, 19 and the parameters of H eff other than were obtained fitting the energy levels of an undistorted CoO 6 cluster (O h symmetry) and calculating the effective hopping between different CoO 6 clusters, 17 following similar ideas that were successful in the superconducting cuprates.…”

Section: Introductionmentioning

confidence: 99%

“…20,21 Summarizing previous results, if is taken as a parameter, a positive has the effect of shrinking the pockets, and for large enough , the pockets disappear from the Fermi surface, reconciling theory with ARPES experiments. 12,13,15 A positive value has been obtained by quantum-chemistry methods 18 and a negative one is obtained fitting the LDA dispersion with H eff . 9,10 Thus the origin of the discrepancy between different methods and the actual value of remains a subject of interest.…”

Section: Introductionmentioning

confidence: 99%

“…7,8 To explain the discrepancy, several calculations including correlation effects were made. [9][10][11][12][13][14][15] These studies used an effective model H eff for the t 2g 3d states of Co, split by the trigonal crystal field into an a 1g singlet and an e g doublet. 16 Except for some simplifications used in the different works, H eff has the form …”

Section: Introductionmentioning

confidence: 99%

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Effect of covalency and interactions on the trigonal splitting in NaxCoO2

Aligia

2013

Phys. Rev. B

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We calculate the effective trigonal crystal field that splits the t 2g levels of effective models for Na x CoO 2 as the local symmetry around a Co ion is reduced from O h to D 3d . To this end, we solve numerically a CoO 6 cluster containing a Co ion with all 3d states and their interactions included, and its six nearest-neighbor O atoms, with the geometry of the system, in which the CoO 6 octahedron is compressed along a C 3 axis. We obtain ≈ 130 meV, with the sign that agrees with previous quantum chemistry calculations but disagrees with first-principles results in the local density approximation (LDA). We find that is very sensitive to a Coulomb parameter that controls the Hund coupling and charge distribution among the d orbitals. The origin of the discrepancy with LDA results is discussed.

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Section: Summary and Discussionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effect of covalency and interactions on the trigonal splitting in NaxCoO2

Aligia

2013

Phys. Rev. B

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Accessing topological superconductivity via a combined STM and renormalization group analysis

et al. 2015

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The search for topological superconductors has recently become a key issue in condensed matter physics, because of their possible relevance to provide a platform for Majorana bound states, non-Abelian statistics, and quantum computing. Here we propose a new scheme which links as directly as possible the experimental search to a material-based microscopic theory for topological superconductivity. For this, the analysis of scanning tunnelling microscopy, which typically uses a phenomenological ansatz for the superconductor gap functions, is elevated to a theory, where a multi-orbital functional renormalization group analysis allows for an unbiased microscopic determination of the material-dependent pairing potentials. The combined approach is highlighted for paradigmatic hexagonal systems, such as doped graphene and water-intercalated sodium cobaltates, where lattice symmetry and electronic correlations yield a propensity for a chiral singlet topological superconductor. We demonstrate that our microscopic material-oriented procedure is necessary to uniquely resolve a topological superconductor state.

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Functional renormalization group for multi-orbital Fermi surface instabilities

Platt

Hanke

Thomale

2013

Advances in Physics

197

253

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Technological progress in material synthesis, as well as artificial realization of condensed matter scenarios via ultra-cold atomic gases in optical lattices or epitaxial growth of thin films, is opening the gate to investigate a plethora of unprecedented strongly correlated electron systems. In a large subclass thereof, a metallic state of layered electrons undergoes an ordering transition below some temperature into unconventional states of matter driven by electronic correlations, such as magnetism, superconductivity, or other Fermi surface instabilities. While this type of phenomena has been a well-established direction of research in condensed matter for decades, the variety of today's accessible scenarios pose fundamental new challenges to describe them. A core complication is the multi-orbital nature of the low-energy electronic structure of these systems, such as the multi-d orbital nature of electrons in iron pnictides and transition-metal oxides in general, but also electronic states of matter on lattices with multiple sites per unit cell such as the honeycomb or kagome lattice. In this review, we propagate the functional renormalization group (FRG) as a suited approach to investigate multi-orbital Fermi surface instabilities. The primary goal of the review is to describe the FRG in explicit detail and render it accessible to everyone both at a technical and intuitive level. Summarizing recent progress in the field of multi-orbital Fermi surface instabilities, we illustrate how the unbiased fashion by which the FRG treats all kinds of ordering tendencies guarantees an adequate description of electronic phase diagrams and often allows to obtain parameter trends of sufficient accuracy to make qualitative predictions for experiments. This review includes detailed and illustrative illustrations of magnetism and, in particular, superconductivity for the iron pnictides from the viewpoint of FRG. Furthermore, it discusses candidate scenarios for topological bulk singlet superconductivity and exotic particle-hole condensates on hexagonal lattices such as sodium-doped cobaltates, graphene doped to van Hove filling, and the kagome Hubbard model. In total, the FRG promises to be one of the most versatile and revealing numerical approaches to address unconventional Fermi surface instabilities in future fields of condensed matter research.

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Dynamical Mean Field Theory of an Effective Three-Band Model forNaxCoO2

Cited by 21 publications

References 35 publications

Effect of covalency and interactions on the trigonal splitting in NaxCoO2

Effect of covalency and interactions on the trigonal splitting in NaxCoO2

Accessing topological superconductivity via a combined STM and renormalization group analysis

Functional renormalization group for multi-orbital Fermi surface instabilities

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