Different doping from apical and planar oxygen vacancies in Ba<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>CuO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>4</mml:mn><mml:mo>−</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:math>and La<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:

Jarlborg, T.; Barbiellini, B.; Markiewicz, R. S.; Bansil, Arun

doi:10.1103/physrevb.86.235111

Cited by 16 publications

(19 citation statements)

References 35 publications

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“…This study reveals that this cuprate has quite unexpected features: ( i ) the apical oxygen distance can be extraordinarily shorter than that known for all other cuprate superconductors so far; ( ii ) a unique compressed version of the local octahedron becomes available; and ( iii ) HTS is realized at very high-hole doping level, contrary to the value of p ∼ 0.15 discussed above for the previously known high- T c cuprates. All three characteristics have been thought to be unfavorable for high T c in the previously discovered cuprates (8–19). Therefore, this material is a distinct kind of high- T c cuprate and challenges the established wisdom of HTS.…”

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confidence: 99%

Superconductivity in a unique type of copper oxide

Zhao

Cao

et al. 2019

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

105

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The mechanism of superconductivity in cuprates remains one of the big challenges of condensed matter physics. High-Tc cuprates crystallize into a layered perovskite structure featuring copper oxygen octahedral coordination. Due to the Jahn Teller effect in combination with the strong static Coulomb interaction, the octahedra in high-Tc cuprates are elongated along the c axis, leading to a 3dx2-y2 orbital at the top of the band structure wherein the doped holes reside. This scenario gives rise to 2D characteristics in high-Tc cuprates that favor d-wave pairing symmetry. Here, we report superconductivity in a cuprate Ba2CuO4-y, wherein the local octahedron is in a very exceptional compressed version. The Ba2CuO4-y compound was synthesized at high pressure at high temperatures and shows bulk superconductivity with critical temperature (Tc) above 70 K at ambient conditions. This superconducting transition temperature is more than 30 K higher than the Tc for the isostructural counterparts based on classical La2CuO4. X-ray absorption measurements indicate the heavily doped nature of the Ba2CuO4-y superconductor. In compressed octahedron, the 3d3z2-r2 orbital will be lifted above the 3dx2-y2 orbital, leading to significant 3D nature in addition to the conventional 3dx2-y2 orbital. This work sheds important light on advancing our comprehensive understanding of the superconducting mechanism of high Tc in cuprate materials.

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confidence: 99%

Superconductivity in a unique type of copper oxide

Zhao

Cao

et al. 2019

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

105

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“…[18][19][20] Electronic structure calculations show that the displacement of apical oxygen, due to oxygen defects, changes the spin-phonon coupling 21 and the electronic states near the Fermi level in cuprates. 22 The control of the functional electronic properties via dopant manipulation is of very high interest in manganites 23 and graphene. 24 The focus has been recently addressed to the control of structural nanoscale phase separation into dopant-rich puddles embedded in a dopant-poor background in these complex materials.…”

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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“…Ab-initio LDA-LMTO band calculations are carried out for supercells of R 2 CuO 4±δ , with R=La or Ba (LCO or BCO). In the case of oxygen vacancies in LCO and BCO, the calculations are based on supercells with a total of 112 sites [19]. The supercell is obtained via a 2x2x2 extension of the basic anti-ferromagnetic (AFM) cell, R 32 Cu 16 O 64−nV , where n V is the number of Ovacancies in the cell.…”

Section: B Methods Of Calculationmentioning

confidence: 99%

Effects of Excess or Deficiency of Oxygen Content on the Electronic Structure of High-T c Cuprates

Jarlborg

Bianconi

Barbiellini

et al. 2013

J Supercond Nov Magn

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Band structure calculations are presented for large supercells of Ba 2 CuO 4 (BCO) with O-vacancies in planar or apical positions, and of superoxygenated La 2 CuO 4 (LCO) with oxygen interstitials in the La 2 O 2 layers. It is found that apical oxygen vacancies in BCO act as electron dopants and makes the electronic structure similar to that of hole doped LCO. Excess oxygen interstitials forming wires in the La 2 O 2 layers of LCO are shown to yield a much larger density-of-states at the Fermi energy than for the stoichiometric compound related with a segmentation of the Fermi surface. Anti-ferromagnetic (AFM) spin fluctuations are strengthened by O-vacancies in BCO as well as by oxygen interstitials in LCO, but are strongly suppressed in O-deficient LCO. Our results indicate the complexity of doping by O-vacancies, and by ordered defects that are a significant factor controlling the electronic properties of cuprates.

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Different doping from apical and planar oxygen vacancies in Ba2CuO4−δand La2

Cited by 16 publications

References 35 publications

Superconductivity in a unique type of copper oxide

Superconductivity in a unique type of copper oxide

Fermi surface reconstruction of superoxygenated La2CuO4superconductors with ordered oxygen interstitials

Effects of Excess or Deficiency of Oxygen Content on the Electronic Structure of High-T c Cuprates

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