Scale-free structural organization of oxygen interstitials in La2CuO4+y

Fratini, Michela; Poccia, Nicola; Ricci, Alessandro; Campi, Gaetano; Burghammer, Manfred; Aeppli, G.; Bianconi, A.

doi:10.1038/nature09260

Cited by 272 publications

(402 citation statements)

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“…The details of the methods were published earlier. 37 34 The excess O i 's sit at the interstitial interlayer positions, above the oxygen ion in the CuO 2 plane of the the orthorhombic unit cell, and form 3D ordered puddles below 350 K; see 4 p electrons. Therefore, simple arguments suggest that one Cu-O band becomes unfilled; i.e., E F has to go down relative to the rest of the bands.…”

Section: Methods Of Calculationmentioning

confidence: 99%

“…[10][11][12] Superoxygenated La 2 CuO 4+y , y > 0.08, provides an ideal case to study the phase separation in the optimum doping regime and the role of ordering of oxygen interstitials (O i 's). [33][34][35][36] The O i 's in the rocksalt LaO layer are mobile; because of the large tensile strain in the spacer layers. This is due to the lattice misfit between different layers 16 of Cu-O bonds that is about 4% shorter than its equilibrium value of 1.97Å.…”

Section: Introductionmentioning

confidence: 99%

“…35 Using novel experimental microscopy, scanning nano x-ray diffraction, probing both the real and the k space, the formation of a granular phase in La 2 CuO 4+y has been discovered. Metallic heavily doped puddles, with ordered oxygen interstitials in the spacer layers, are embedded in an oxygen-poor background [34][35][36] at optimal doping. In the heavily doped grains the excess oxygen interstitials are ordered as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Methods Of Calculationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fermi surface reconstruction of superoxygenated La2CuO4superconductors with ordered oxygen interstitials

Jarlborg

Bianconi

2013

Phys. Rev. B

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“…We present experiments that demonstrate that CDW puddles, have a complex spatial distribution and coexist with, but are spatially anticorrelated to, quenched disorder in HgBa 2 CuO 4+y (Hg1201). The sample we studied is a layered perovskite at optimum doping with oxygen interstitials y=0.12, tetragonal symmetry P4/mmm and a low misfit strain [14][15][16] . The X-ray diffraction (XRD) measurements (see Methods) show diffuse CDW satellites (secondary peaks surrounding a main peak) at q CDW =(0.23a*, 0.16c*), in the b*=0 plane and q CDW =(0.23b*, 0.16c*) in the a*=0 plane (where a*, b*, and c* are the reciprocal lattice units) around specific Bragg peaks, such as (1 0 8), below the onset temperature T CDW =240 K (see Fig.…”

mentioning

confidence: 99%

“…To investigate the interplay between the CDW puddles and the quenched disorder, we studied the spatial distribution of oxygen defects. 14,16) shows T c variations, owing to the effect of the spatial organization of O i on superconductivity.…”

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Inhomogeneity of charge-density-wave order and quenched disorder in a high-Tc superconductor

Campi

Bianconi

Poccia

et al. 2015

Nature

300

309

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It has recently been established that the high temperature (high-Tc(between atomic and macroscopic scale). Here we report micro X-ray diffraction imaging of the spatial distribution of both the charge-density-wave 'puddles' (domains with only a few wavelengths) and quenched disorder in HgBa 2 CuO 4+y , the single layer cuprate with the highest T c , 95 kelvin [26][27][28] . We found that the charge-density-wave puddles, like the steam bubbles in boiling water, have a fat-tailed size distribution that is typical of selforganization near a critical point 19 . However, the quenched disorder, which arises from oxygen interstitials, has a distribution that is contrary to the usual assumed random, uncorrelated distribution 12, 13 . The interstitials-oxygen-rich domains are spatially anticorrelated with the charge-density-wave domains, leading to a complex emergent geometry of the spatial landscape for superconductivity. 2Although it is known that the incommensurate charge-density-wave (CDW) order in cuprates (copper oxides) is made of ordered, stripy, nanoscale puddles with an average of only 3-4 oscillations, information about the size distribution and spatial organization of these puddles has so far not been available. We present experiments that demonstrate that CDW puddles, have a complex spatial distribution and coexist with, but are spatially anticorrelated to, quenched disorder in HgBa 2 CuO 4+y (Hg1201). The sample we studied is a layered perovskite at optimum doping with oxygen interstitials y=0.12, tetragonal symmetry P4/mmm and a low misfit strain [14][15][16] . The X-ray diffraction (XRD) measurements (see Methods) show diffuse CDW satellites (secondary peaks surrounding a main peak) at q CDW =(0.23a*, 0.16c*), in the b*=0 plane and q CDW =(0.23b*, 0.16c*) in the a*=0 plane (where a*, b*, and c* are the reciprocal lattice units) around specific Bragg peaks, such as (1 0 8), below the onset temperature T CDW =240 K (see Fig. 1a). The component of the momentum transfer q CDW in the CuO 2 plane (0.23a*) in this case is smaller than it is in the underdoped case (0.28a*) 5 . The temperature evolution of CDW-peak profile along a* (in the h direction; Fig. 1b) shows a smeared, glassy-like evolution below T CDW .The CDW-peak intensity reaches a maximum at T=100 K, followed by a drop associated with the onset of superconductivity at T=T c . We investigated the isotropic character of the CDW, in the a-b plane using azimuthal scans, as shown in Fig. 1c. We observed an equal probability of vertical and horizontally striped CDW puddles.Our main result is the discovery of the statistical spatial distribution of the CDW-puddle size and density throughout the sample, which shows an emergent complex network geometry for the superconducting phase. We performed scanning micro X-ray diffraction (SµXRD) measurements (see Methods) to extend the imaging of spatial inhomogeneity previously obtained by scanning tunneling microscopy [7][8][9] , from the surface to the bulk of the sample and from nanoscale to mesoscale spatial inh...

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Encapsulating High‐Temperature Superconducting Twisted van der Waals Heterostructures Blocks Detrimental Effects of Disorder

et al. 2023

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High‐temperature cuprate superconductors based van der Waals (vdW) heterostructures hold high technological promise. One of the obstacles hindering their progress is the detrimental effect of disorder on the properties of the vdW‐devices‐based Josephson junctions (JJs). Here, a new method of fabricating twisted vdW heterostructures made of Bi2Sr2CuCa2O8+δ, crucially improving the JJ characteristics and pushing them up to those of the intrinsic JJs in bulk samples, is reported. The method combines cryogenic stacking using a solvent‐free stencil mask technique and covering the interface by insulating hexagonal boron nitride crystals. Despite the high‐vacuum condition down to 10−6 mbar in the evaporation chamber, the interface appears to be protected from water molecules during the in situ metal deposition only when fully encapsulated. Comparing the current–voltage curves of encapsulated and unencapsulated interfaces, it is revealed that the encapsulated interfaces’ characteristics are crucially improved, so that the corresponding JJs demonstrate high critical currents and sharpness of the superconducting transition comparable to those of the intrinsic JJs. Finally, it is shown that the encapsulated heterostructures are more stable over time.

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Scale-free structural organization of oxygen interstitials in La2CuO4+y

Cited by 272 publications

References 29 publications

Fermi surface reconstruction of superoxygenated La2CuO4superconductors with ordered oxygen interstitials

Fermi surface reconstruction of superoxygenated La2CuO4superconductors with ordered oxygen interstitials

Inhomogeneity of charge-density-wave order and quenched disorder in a high-Tc superconductor

Encapsulating High‐Temperature Superconducting Twisted van der Waals Heterostructures Blocks Detrimental Effects of Disorder

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