The strain of CuO<sub>2</sub>lattice: the second variable for the phase diagram of cuprate perovskites

Agrestini, S.; Saini, N. L.; Bianconi, Ginestra; Bianconi, A.

doi:10.1088/0305-4470/36/35/302

Cited by 84 publications

(100 citation statements)

References 54 publications

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“…While present in all cuprates [19][20][21][22][23], it is not well understood so that its consequences for the various experimental probes are not clear. In NMR, one finds various degrees of line broadening in the various cuprates (see e.g., [24]) typically caused by concomitant charge and spin density variations [25].…”

Section: Introductionmentioning

confidence: 99%

Contrasting Phenomenology of NMR Shifts in Cuprate Superconductors

2017

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Nuclear magnetic resonance (NMR) shifts, if stripped of their uncertainties, must hold key information about the electronic fluid in the cuprates. The early shift interpretation that favored a single-fluid scenario will be reviewed, as well as recent experiments that reported its failure. Thereafter, based on literature shift data for planar Cu, a contrasting shift phenomenology for cuprate superconductors is developed, which is very different from the early view while being in agreement with all published data. For example, it will be shown that the hyperfine scenario used up to now is inadequate as a large isotropic shift component is discovered. Furthermore, the changes of the temperature dependences of the shifts above and below the superconducting transitions temperature proceed according to a few rules that were not discussed before. It appears that there can be substantial spin shift at the lowest temperature if the magnetic field is perpendicular to the CuO 2 plane, which points to a localization of spin in the 3d(x 2 − y 2 ) orbital. A simple model is presented based on the most fundamental findings. The analysis must have new consequences for theory of the cuprates.

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Section: Introductionmentioning

confidence: 99%

Contrasting Phenomenology of NMR Shifts in Cuprate Superconductors

2017

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“…For many years the dominant theories of HTS have considered a stoichiometric CuO 2 layer and have neglected the key role of lattice effects (16,17), even if the ½CuO 2 ∞ layers are intercalated by a variety of defective oxide AO layers (A=La, Ba, Sr, Ca, Y, Hg or Rare earths) with a large tolerance factor (18) or misfit strain (19,20) and a large number of oxygen interstitials or defects. The lattice misfit induces tilting and corrugation of the ½CuO 2 ∞ layers and structural phase transitions going from I4∕mmm (high temperature tetragonal), Bmab, Pccn, and Fmmm (low temperature orthorhombic, LTO) to P4 2 ∕ncm (low temperature tetragonal) in systems like La 2 CuO 4 (21).…”

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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.

113

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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“…We note that the above considerations have focused on average bond distances and bond angles. There exists ample evidence from local bulk probes that the cuprates exhibit significant compound-specific local deviations from the average crystal structure [41,42], and that the charge distributions in both LSCO [43] and Hg1201 [44] vary on the nanoscale. Based on modeling the disorder in the interstitial layers, it was concluded that the hole mean free path and the screening of the Coulomb repulsion in Hg1201 are substantially larger than in LSCO, hence contributing to the higher T c [39].…”

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confidence: 99%

Strain derivatives ofTcin HgBa2CuO4+δ: The CuO
Wang
¹
,
Zhang
²
,
Yan
³

et al. 2014
Phys. Rev. B

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The strain derivatives of Tc along the a and c axes have been determined for HgBa2CuO 4+δ (Hg1201), the simplest monolayer cuprate with the highest Tc of all monolayer cuprates (Tc = 97 K at optimal doping). The underdoped compound with the initial Tc of 65 K has been studied as a function of pressure up to 20 GPa by magnetic susceptibility and X-ray diffraction (XRD). The observed linear increase in Tc with pressure is the same as previously been found for the optimally-doped compound. The above results have enabled the investigation of the origins of the significantly different Tc values of optimally doped Hg1201 and the well-studied compound La2−xSrxCuO4 (LSCO), the latter value of Tc = 40 K being only about 40% of the former. Hg1201 can have almost identical CuO6 octahedra as LSCO if specifically strained. When the apical and inplane CuO2 distances are the same for the two compounds, a large discrepancy in their Tc remains. Differences in crystal structures and interactions involving the Hg-O charge reservoir layers of Hg1201 may be responsible for the different Tc values exhibited by the two compounds.

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The strain of CuO₂lattice: the second variable for the phase diagram of cuprate perovskites

Abstract: We show the key role of the elastic local strain (or micro-strain) ε of the CuO 2 lattice in the phase diagram of cuprate superconductors. The superconducting critical temperature T c (δ, ε) is shown to be a function of two variables, the doping δ and the microstrain ε.

Cited by 84 publications

References 54 publications

Contrasting Phenomenology of NMR Shifts in Cuprate Superconductors

Contrasting Phenomenology of NMR Shifts in Cuprate Superconductors

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

Strain derivatives ofTcin HgBa2CuO4+δ: The CuO
Wang
¹
,
Zhang
²
,
Yan
³

et al. 2014
Phys. Rev. B

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The strain of CuO2lattice: the second variable for the phase diagram of cuprate perovskites

Abstract: We show the key role of the elastic local strain (or micro-strain) ε of the CuO 2 lattice in the phase diagram of cuprate superconductors. The superconducting critical temperature T c (δ, ε) is shown to be a function of two variables, the doping δ and the microstrain ε.

Cited by 84 publications

References 54 publications

Contrasting Phenomenology of NMR Shifts in Cuprate Superconductors

Contrasting Phenomenology of NMR Shifts in Cuprate Superconductors

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

Strain derivatives ofTcin HgBa2CuO4+δ: The CuOWang1, Zhang2, Yan3 et al. 2014Phys. Rev. B

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The strain of CuO₂lattice: the second variable for the phase diagram of cuprate perovskites

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

Strain derivatives ofTcin HgBa2CuO4+δ: The CuO
Wang
¹
,
Zhang
²
,
Yan
³

et al. 2014
Phys. Rev. B