Model for phase separation controlled by doping and the internal chemical pressure in different cuprate superconductors

Кugel, K. I.; Rakhmanov, A. L.; Sboychakov, A. O.; Poccia, Nicola; Bianconi, A.

doi:10.1103/physrevb.78.165124

Cited by 79 publications

(89 citation statements)

References 41 publications

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“…Our quantitative results should be tested against theories of composite, granular superconductors proposed for cuprates (10,14,15,25,(30)(31)(32)(55)(56)(57)(58)(59)(60)(61)(62). The X-ray data indicate that these theories must take into account not only the usual superconducting proximity effects, but also the effects of the strains the two components exert on each other.…”

Section: Discussionmentioning

confidence: 99%

Optimum inhomogeneity of local lattice distortions in La ₂ CuO _{4+
y}

Poccia

Ricci

Campi

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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112

140

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Electronic functionalities in materials from silicon to transition metal oxides are, to a large extent, controlled by defects and their relative arrangement. Outstanding examples are the oxides of copper, where defect order is correlated with their high superconducting transition temperatures. The oxygen defect order can be highly inhomogeneous, even in optimal superconducting samples, which raises the question of the nature of the sample regions where the order does not exist but which nonetheless form the "glue" binding the ordered regions together. Here we use scanning X-ray microdiffraction (with a beam 300 nm in diameter) to show that for La 2 CuO 4þy , the glue regions contain incommensurate modulated local lattice distortions, whose spatial extent is most pronounced for the best superconducting samples. For an underdoped single crystal with mobile oxygen interstitials in the spacer La 2 O 2þy layers intercalated between the CuO 2 layers, the incommensurate modulated local lattice distortions form droplets anticorrelated with the ordered oxygen interstitials, and whose spatial extent is most pronounced for the best superconducting samples. In this simplest of high temperature superconductors, there are therefore not one, but two networks of ordered defects which can be tuned to achieve optimal superconductivity. For a given stoichiometry, the highest transition temperature is obtained when both the ordered oxygen and lattice defects form fractal patterns, as opposed to appearing in isolated spots. We speculate that the relationship between material complexity and superconducting transition temperature T c is actually underpinned by a fundamental relation between T c and the distribution of ordered defect networks supported by the materials. granular superconductors | multiband superconductivity in density wave metals | scale-free heterogeneity | imaging phase separation | X-ray illumination

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Section: Discussionmentioning

confidence: 99%

Optimum inhomogeneity of local lattice distortions in La ₂ CuO _{4+
y}

Poccia

Ricci

Campi

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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112

140

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“…The cuprates at optimum doping present the second type of phase separation as we have proposed before. 74,75 Recently it has been found that some cuprate systems like La 2 CuO 4.1 show scale invariance of the distribution of oxygen interstitials that suggests a scale invariant phase separation typical of a system near the critical point. Therefore, it is possible that the criticality in La 2 CuO 4+y results from a quantum critical point.…”

Section: -70mentioning

confidence: 99%

“…The upper Hubbard sub-bands are empty, and we can proceed to the limit U α , U ′ → ∞. In this case, the one-particle Green's function is independent of U and can be written in the form 51,74 …”

Section: The Modelmentioning

confidence: 99%

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Intrinsic arrested nanoscale phase separation near a topological Lifshitz transition in strongly correlated two-band metals

Bianconi¹,

Poccia²,

Sboychakov³

et al. 2015

Supercond. Sci. Technol.

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The arrested nanoscale phase separation in a two-band Hubbard model for strongly correlated charge carriers is shown to occur in a particular range in vicinity of the topological Lifshitz transition, where the Fermi energy crosses the bottom of the narrow band and a new sheet of the Fermi surface related to the charge carriers of the second band comes into play. We determine the phase separation diagram of this two-band Hubbard model as a function of two variables, the charge carrier density and the energy shift between the chemical potential and the bottom of the second band. In this phase diagram, we first determine a line of quantum critical points for the Lifshitz transition and find criteria for the electronic phase separation resulting in an inhomogeneous charge distribution. Finally, we identify the critical point in presence of a variable long-range Coulomb interaction where the scale invariance of the coexisting phases with different charge densities appears. We argue that this point is relevant for the regime of scale invariance of the nanoscale phase separation in cuprates like it was first observed in La2CuO4.1.

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“…4 In the underdoped regime the homogeneous metallic phase competes with electronic phase separation with the formation of a complex heterogeneous phase. [5][6][7][8] The chargespin ordering and electronic phase separation are accompanied by fluctuations of the local structure that diverges from the average structure. [9][10][11][12][13][14] The defects inserted in the spacer layers to dope the copper oxide electronic structure are an additional source for the modulation of the heterogeneous electronic states near the Fermi level.…”

Section: Introductionmentioning

confidence: 99%

Fermi surface reconstruction of superoxygenated La2CuO4superconductors with ordered oxygen interstitials

Jarlborg

Bianconi

2013

Phys. Rev. B

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Novel imaging methods show that the mobile dopants in optimum doped La 2 CuO 4+y (LCO) get self-organized, instead of randomly distributed, to form an inhomogeneous network of nanoscale metallic puddles with ordered oxygen interstitials interspersed with oxygen-depleted regions. These puddles are expected to be metallic, being far from half filling because of high dopant density, and to sustain superconductivity having a size in the range 5-20 nm. However, the electronic structure of these heavily doped metallic puddles is not known. In fact the rigid-band model fails because of ordering of dopants and supercell calculations are required to obtain the Fermi surface reconstruction. We have performed advanced band calculations for a large supercell La 16 Cu 8 O 32+N where N = 1 or 2 oxygen interstitials form rows in the spacer La 16 O 16+N layers intercalated between the CuO 2 layers as determined by scanning nano x-ray diffraction. The additional occupied states made by interstitial oxygen orbitals sit well below the Fermi level (E F ) and lead to hole doping as expected. The unexpected results show that in the heavily doped puddles the altered Cu(3d)-O(2p) band hybridization at E F induces a multiband electronic structure with the formation of multiple Fermi surface spots: (a) Small gaps appear in the folded Fermi surface, (b) three minibands cross E F with reduced Fermi energies of 60, 150, and 240 meV, respectively, (c) the density of states and band mass at E F show substantial increases, and (d) spin-polarized calculations show a moderate increase of antiferromagnetic spin fluctuations. All calculated features are favorable to enhance superconductivity; however, the comparison with experimental methods probing the average electronic structure of cuprates will require the description of the electronics of a network of multigap superconducting puddles.

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Model for phase separation controlled by doping and the internal chemical pressure in different cuprate superconductors

Cited by 79 publications

References 41 publications

Optimum inhomogeneity of local lattice distortions in La ₂ CuO _{4+
y}

Optimum inhomogeneity of local lattice distortions in La ₂ CuO _{4+
y}

Intrinsic arrested nanoscale phase separation near a topological Lifshitz transition in strongly correlated two-band metals

Fermi surface reconstruction of superoxygenated La2CuO4superconductors with ordered oxygen interstitials

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Model for phase separation controlled by doping and the internal chemical pressure in different cuprate superconductors

Cited by 79 publications

References 41 publications

Optimum inhomogeneity of local lattice distortions in La 2 CuO 4+ y

Optimum inhomogeneity of local lattice distortions in La 2 CuO 4+ y

Intrinsic arrested nanoscale phase separation near a topological Lifshitz transition in strongly correlated two-band metals

Fermi surface reconstruction of superoxygenated La2CuO4superconductors with ordered oxygen interstitials

Contact Info

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Optimum inhomogeneity of local lattice distortions in La ₂ CuO _{4+
y}

Optimum inhomogeneity of local lattice distortions in La ₂ CuO _{4+
y}