Order-parameter symmetries in high-temperature superconductors

Klemm, Richard A.; Rieck, C. T.; Scharnberg, K.

doi:10.1103/physrevb.61.5913

Cited by 40 publications

(41 citation statements)

References 48 publications

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“…4 in Ref. [27]) experiments, as well as theoretical considerations [28]. It is important to note that due to the reasons described above the saturation of λ −2 c (T ) obtained here has not been observed in LFM experiments [19].…”

Section: Is the Maximum Value Of The Gap And (T ϕ) = 0˜ (T /T C )Gmentioning

confidence: 93%

s-Wave Symmetry Along the c-Axis and s+d In-plane Superconductivity in Bulk YBa2Cu4O8

Khasanov

Shengelaya

Karpiński

et al. 2007

J Supercond Nov Magn

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To clarify the order parameter symmetry of cuprates, the magnetic penetration depth λ was measured along the crystallographic directions a, b, and c in single crystals of YBa 2 Cu 4 O 8 via muon spin rotation. This method is direct, bulk sensitive, and unambiguous. The temperature dependences of λ −2 a and λ −2 b exhibit an inflection point at low temperatures as is typical for two-gap superconductivity (TGS) with s + d-wave character in the planes. Perpendicular to the planes a pure s-wave gap is observed thereby highlighting the important role of c-axis effects. We conclude that these are generic and universal features in the bulk of cuprates. Recently, new muon spin rotation (μSR) investigations of single crystal La 1.83 Sr 0.17 CuO 4 detected an inflection point in the temperature dependence of the inverse-squared in-plane magnetic penetration depth λ −2 ab , which is a direct consequence of two superconducting gaps with largely different zero temperature gap values [14]. Since it is unclear whether these observations are a material specific property or generic and intrinsic to HTS, the previous μSR studies were extended to single crystal YBa 2 Cu 4 O 8 and were performed by applying a magnetic field along the crystallographic directions a, b, and c. Thereby we obtain the three principle components of the second moments of the local magnetic field distribution P (B) in the mixed state, which are related to the superfluid density, and reflect directly the corresponding penetration depths λ a , λ b , and λ c . While λ −2 a and λ −2 b vary almost linearly with temperature for 20 < T < 50 K, as is expected for a d-wave order parameter, the c-axis response (λ −2 c ) saturates below 30 K, as expected for a s-wave order parameter. In addition, λ −2 a and PACS

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Section: Is the Maximum Value Of The Gap And (T ϕ) = 0˜ (T /T C )Gmentioning

confidence: 93%

s-Wave Symmetry Along the c-Axis and s+d In-plane Superconductivity in Bulk YBa2Cu4O8

Khasanov

Shengelaya

Karpiński

et al. 2007

J Supercond Nov Magn

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“…Hence, orthorhombicity cannot explain the data of Li et al [6]. OP increases in amplitude, so that the overall OP effectively rotates near the twist junction [8]. However, the amount of twisting is strongly limited by the second bare transition temperature T 0 cB and by the bulk and twist junction Josephson coupling strengths η, η ′ .…”

Section: The Twist Theorem and Its Consequencesmentioning

confidence: 44%

“…For YBCO with point group C 1 2v , the mirror planes σ x , σ y (the ac, bc planes) contain the crystal axes a and b along the Cu-O bond direction in the CuO 2 layers. In BSCCO with approximate point group C 13 2v , the mirror plane σ b (the bc-plane) contains the b crystal axis (along a diagonal between the Cu-O bond directions) and the periodic lattice distortion [7,8]. The irreducible representations for the OPs in YBCO and BSCCO are given in Table I.…”

Section: Group Theory and The Fermi Surfacementioning

confidence: 99%

Bi2Sr2CaCu2O8+$delta; bicrystal c-axis twist Josephson junctions: a new phase-sensitive test of order parameter symmetry

Klemm¹

2003

Physica B: Condensed Matter

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Li et al. [Phys. Rev. Lett. 83, 4160 (1999)] prepared atomically clean Bi2Sr2CaCu2O 8+δ (BSCCO) Josephson junctions between identical single crystal cleaves stacked and twisted an angle φ0 about the c-axis. For each bicrystal, the ratio J J c /J S c of the c axis twist junction critical current density to that across either single crystal part is unity, independent of φ0 and the ratio A J /A S of junction areas. From extensive theoretical studies involving a variety of tunneling and superconducting order parameter (OP) forms, we conclude that the results provide strong evidence for incoherent c-axis tunneling and that the dominant OP is s-wave for T ≤ Tc. Recently, Takano et al. [Phys. Rev. B 65, 140513(R) (2002)] obtained results from BSCCO whisker twist junctions which also rule out a pure d-wave OP, but which are surprisingly suggestive of coherent c-axis tunneling from small Fermi surface hot spots.

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“…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) they assume that the cuprate-planes superconduct, and (ii) faced with the fact that their data do not exhibit the expected U-shape (with a sharper U than BiO's expected for s-wave superconductivity), they postulate that they have evidence of d-wave superconductivity. But the work of Klemm [6] and Li [7] provides a convincing demonstration that the superconductivity in Bi 2 Sr 2 CaCu 2 O 8 is s-wave in character, and we have found [8], using the bulk probe of muon spectroscopy, that the superconductivity of YBa 2 Cu 3 O 7 is also s-wave in character with an uncertainty of less than 4×10 −6 . It is exceedingly unlikely that, in the bulk, YBa 2 Cu 3 O 7 could have swave pairing, while Bi 2 Sr 2 CaCu 2 O 8 has d-wave [4] (which cannot be reconciled with other measurements [9]).…”

Section: Faulty Evidence For Cuprate-plane Superconductivitymentioning

confidence: 99%

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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Order-parameter symmetries in high-temperature superconductors

Cited by 40 publications

References 48 publications

s-Wave Symmetry Along the c-Axis and s+d In-plane Superconductivity in Bulk YBa2Cu4O8

s-Wave Symmetry Along the c-Axis and s+d In-plane Superconductivity in Bulk YBa2Cu4O8

Bi2Sr2CaCu2O8+$delta; bicrystal c-axis twist Josephson junctions: a new phase-sensitive test of order parameter symmetry

High-temperature superconductivity

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