Structural anomalies, oxygen ordering and superconductivity in oxygen deficient Ba2YCu3Ox

Cava, R. J.; Hewat, A.W.; Hewat, E.A.; Batlogg, B.; Marezio, M.; Rabe, Karin M.; Krajewski, J. J.; Peck, W. F.; Rupp, L. W.

doi:10.1016/0921-4534(90)90376-p

Cited by 1,081 publications

(323 citation statements)

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“…Only the single datum near x=6.4 from Ref. [1] deviates significantly from a straight line, and the corresponding data of Ref. [2] define a straight line without a jump for x > 6.3.…”

Section: Charge Transfer In Cupratesmentioning

confidence: 99%

“…The jump in the Ref. [1] data, which is non-existent in the data of Ref. [2], is the basis for the argument that the superconductivity is in the cuprate-planes.…”

Section: Charge Transfer In Cupratesmentioning

confidence: 99%

“…Note that in Ref. [1] a smooth line through the data was displayed. Note that the two data sets differ because of a difference in calibration (which should be ignored).…”

Section: Charge Transfer In Cupratesmentioning

confidence: 99%

“…Two of the most-cited papers in contemporary physics claim to show that the cuprate-planes of YBa 2 Cu 3 O x superconduct [1,2]. However, there are problems with both papers that have not been well-recognized: (i) the evidence of superconductivity in the cuprate-planes comes from a jump in charge which was evident in the work of Cava et al, but not in the work of Jorgensen et al; and (ii) the studies of Jorgensen et al claim to confirm the data of Cava et al, but actually do not in the most important way: Jorgensen does not have the Cava jump.…”

Section: Faulty Evidence For Cuprate-plane Superconductivitymentioning

confidence: 99%

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High-temperature superconductivity

Dow¹,

Harshman²

2003

Braz. J. Phys.

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The widely held notion that high-temperature superconductivity originates in the cuprate-planes is proven to be faulty. In the cuprates such as YBa2Cu3O7, we argue that the superconductivity resides in the BaO layers. This superconductivity is s-wave, not d-wave, in the bulk. The trio of ruthenate compounds, doped Sr 2 YRuO 6 , GdSr2Cu2RuO8, and Gd2−zCezSr2Cu2RuO10 all superconduct in their SrO layers, which is why they have almost the same ∼49 K onset temperatures for superconductivity. Faulty evidence for cuprate-plane superconductivityTwo of the most-cited papers in contemporary physics claim to show that the cuprate-planes of YBa 2 Cu 3 O x superconduct [1,2]. However, there are problems with both papers that have not been well-recognized: (i) the evidence of superconductivity in the cuprate-planes comes from a jump in charge which was evident in the work of Cava et al., but not in the work of Jorgensen et al.; and (ii) the studies of Jorgensen et al. claim to confirm the data of Cava et al., but actually do not in the most important way: Jorgensen does not have the Cava jump. In fact, a closer examination of the data reveals that only one datum is responsible for the jump in charge that is purportedly evidence for cuprate-plane superconductivity, and this datum was not reproduced in the data of Jorgensen et al. or (to our knowledge) elsewhere. This startling fact has been missed by many people because a continuous line was drawn through rather sparse data and conveyed the impression that the data are much denser than they are. In other words, the concept of cuprate-plane superconductivity has not been confirmed and rests on only one unreproduced datum. (See Fig. 1.) This is important to realize because the superconducting layers in most (and perhaps all) high-temperature superconductors are not the cuprate-planes, as was implied by the now-infamous fictitious jump in cuprate-plane Cu charge [3].Perhaps an independent confirmation of the problem with cuprate-plane superconductivity comes from the scanning tunneling microscopy data on Bi 2 Sr 2 CaCu 2 O 8 of the Illinois group [4,5]. (See Fig. 2). The surface layer of this compound, when it is cleaved, is the BiO layer. Underneath that is the SrO layer, and then a CuO 2 plane; after that comes a Ca layer and a second CuO 2 plane. Apparently the Illinois workers have imaged the BiO surface layer, and then a CuO 2 layer that is exposed by a step protruding from the side of the sample, apparently the second CuO 2 layer beneath the surface. An examination of their data reveals that their BiO layer looks like most others, with a U-shaped feature that is indicative of a layer nearby a superconducting layer. But their protruding CuO 2 plane does not look at all like a superconductor, and instead of a U-shaped feature, seems to have a band-gap with no density of states in the gap. The Illinois workers have interpreted their observations as evidence of dwave superconductivity in the cuprate-planes, but this interpretation is based primarily on the facts that (i) the...

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“…Only the single datum near x=6.4 from Ref. [1] deviates significantly from a straight line, and the corresponding data of Ref. [2] define a straight line without a jump for x > 6.3.…”

Section: Charge Transfer In Cupratesmentioning

confidence: 99%

“…The jump in the Ref. [1] data, which is non-existent in the data of Ref. [2], is the basis for the argument that the superconductivity is in the cuprate-planes.…”

Section: Charge Transfer In Cupratesmentioning

confidence: 99%

“…Note that in Ref. [1] a smooth line through the data was displayed. Note that the two data sets differ because of a difference in calibration (which should be ignored).…”

Section: Charge Transfer In Cupratesmentioning

confidence: 99%

Section: Faulty Evidence For Cuprate-plane Superconductivitymentioning

confidence: 99%

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High-temperature superconductivity

Dow¹,

Harshman²

2003

Braz. J. Phys.

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“…The broad implication of this result is that superconducting Na x CoO 2 •4xD 2 O (x≈1/3) can be viewed as a stacking of superconducting CoO 2 layers separated by Na x (D 2 O) 4x charge reservoir layers with the potential for charge transfer between the charge reservoir and the supercconducting layers, much like the layered copper oxides. [16,17] …”

Section: Introductionmentioning

confidence: 99%

Thermal expansion and compressibility in superconductingNaxCoO2∙4xD2O
Jorgensen
¹
,
Avdeev²,
Hinks³
et al. 2005
Phys. Rev. B
6
0
0
0
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We have performed thermal expansion and compressibility measurements on the recently discovered superconducting material Na x CoO 2 •4xD 2 O (x≈1/3) using neutron powder diffraction over the temperature range 10-295 K and the pressure range 0-0.6 GPa. Pressure measurements were done in a helium-gas pressure cell. Both the thermal expansion and compressibility are very anisotropic, with the largest effects along the c axis, as would be expected for a layered material with weak hydrogen bonding nominally along the c axis. Near room temperature, the anisotropies of the thermal expansion and compressibility of the hexagonal crystal structure are nearly the same [(∆c/c)/(∆a/a)≈3-4], with a 100° C change in temperature being roughly equivalent to 0.2 GPa pressure. This would imply that changes in atom position parameters are also the same, but this is not the case. While the effects of temperature on the atom positions are essentially what one might expect, the effects of pressure are surprising. With increasing pressure, the thickness of the CoO 2 layer increases, due to the combined effects of an increasing Co-O bond length and changes in the O-Co-O angles of the CoO 6 octahedra. We conclude that this unusual effect results from pressure-induced strengthening of the hydrogen bonding between the Na x (D 2 O) 4x layers and the CoO 2 layers. The strengthening of these hydrogen bonds requires that charge be moved from the somewhere else in the structure; hence, there is a pressure induced charge redistribution that weakens (lengthens) the Co-O bonds and changes the electronic structure of the superconducting CoO 2 layers.

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Decrease of Bulk Pinning Strength in Deoxygenated YBCO Single Crystals

Moreno

Bekeris

2000

phys. stat. sol. (b)

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We measured the first and third harmonics of the complex ac susceptibility in YBCO single crystals with different oxygen contents (6.5 ≤ x ≤ 7). The amplitude of the ac field was varied in presence of an external dc field both applied parallel to the c‐axis of the crystals. We give evidence that deoxygenation leads to a reduction of the bulk pinning strength and consequently to a stronger contribution of geometrical barriers. These results support the recently reported investigations showing that deoxygenation makes the YBCO crystals more anisotropic reducing the effective bulk pinning for quasi‐two‐dimensional vortices. We also show measurements for the same crystals with the ac field applied perpendicular to the c‐axis.

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Structural anomalies, oxygen ordering and superconductivity in oxygen deficient Ba2YCu3Ox

Cited by 1,081 publications

References 24 publications

High-temperature superconductivity

High-temperature superconductivity

Thermal expansion and compressibility in superconductingNaxCoO2∙4xD2O
Jorgensen
¹
,
Avdeev²,
Hinks³
et al. 2005
Phys. Rev. B
6
0
0
0
View full text Add to dashboard Cite

Decrease of Bulk Pinning Strength in Deoxygenated YBCO Single Crystals

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Structural anomalies, oxygen ordering and superconductivity in oxygen deficient Ba2YCu3Ox

Cited by 1,081 publications

References 24 publications

High-temperature superconductivity

High-temperature superconductivity

Thermal expansion and compressibility in superconductingNaxCoO2∙4xD2OJorgensen1, Avdeev2, Hinks3 et al. 2005Phys. Rev. B6000View full textAdd to dashboardCite

Decrease of Bulk Pinning Strength in Deoxygenated YBCO Single Crystals

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Product

Resources

About

Thermal expansion and compressibility in superconductingNaxCoO2∙4xD2O
Jorgensen
¹
,
Avdeev²,
Hinks³
et al. 2005
Phys. Rev. B
6
0
0
0
View full text Add to dashboard Cite