Low Temperature Penetration Depth Measurements in High-T c Superconductors

Panagopoulos, C.; Xiang, Tao; Cooper, J. R.; Tallon, J. L.

doi:10.1007/978-4-431-66874-9_27

Cited by 3 publications

(4 citation statements)

References 15 publications

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“…Such deviations are a direct consequence of a well-established fact: on the overdoped side of the phase diagram dc increases, whereas c is either unchanged or may show a minor increase. 10,16,37 We find a similar scaling pattern between c and dc in other classes of layered superconductors, including organic materials, transition metal dichalcogenides and Sr 2 RuO 4 ͑Fig. 2͒.…”

Section: Universal C-axis Plotsupporting

confidence: 58%

Global trends in the interplane penetration depth of layered superconductors

et al. 2002

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We report on generic trends in the behavior of the interlayer penetration depth c of several different classes of quasi-two-dimensional superconductors including high-T c cuprates, Sr 2 RuO 4 , transition-metal dichalcogenides and organic materials of the (BEDT-TTF) 2 X series. An analysis of these trends reveals two distinct patterns in the scaling between the values of c and the magnitude of the c-axis dc conductivity dc : one realized in the systems with a ground state formed from well-defined quasiparticles, and the other seen in systems in which the quasiparticles are not well defined. The latter pattern is found primarily in underdoped cuprates, and indicates a dramatic enhancement ͑a factor Ӎ10 2 ) of the energy scale ⍀ C associated with the formation of the condensate compared to the data for conventional materials. We discuss the implication of these results on the understanding of superconductivity in high-T c cuprates.

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Section: Universal C-axis Plotsupporting

confidence: 58%

Global trends in the interplane penetration depth of layered superconductors

et al. 2002

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“…By removing oxygen from YBCO 7 one can significantly reduce the chain contribution. YBCO 6.57 has an anisotropy ratio g ͓l c ͑0͒͞l ab ͑0͔͒ ϳ 25 [28]. As in Hg-1201, Hg-1223, and YBCO 7 , l ab ͑T ͒ in YBCO 6.57 is linear at low temperatures but with a slope 20 Å͞K.…”

mentioning

confidence: 93%

“…As in Hg-1201, Hg-1223, and YBCO 7 , l ab ͑T ͒ in YBCO 6.57 is linear at low temperatures but with a slope 20 Å͞K. The systematic variation of l ab with oxygen content in YBCO will be discussed separately [28]. Here we focus on l c ͑T͒ of YBCO 6.57 , Fig.…”

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confidence: 97%

Probing the Order Parameter and thec-Axis Coupling of High-TcCuprates by Penetration Depth Measurements

et al. 1997

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We have measured the low-temperature ͑T ͒ dependence of the anisotropic penetration depth l͑T ͒ of magnetically aligned powders of HgBa 2 Ca n21 Cu n O 2n121d (n 1 and 3) down to 1.2 K. For both members the T dependence of the in-plane penetration depth l ab ͑T ͒ is strongly linear, whereas the outof-plane component l c ͑T͒, for n 1 and 3, varies as T 5 and T 2 , respectively. For comparison, we also report l c ͑T͒ data for grain-aligned YBa 2 Cu 3 O 72d (d 0.0 and 0.43) which vary as T and T 2 , respectively. The results are discussed in terms of d x 2 -y 2 -wave symmetry of the order parameter in cuprates.[S0031-9007 (97)04087-8] PACS numbers: 74.25.Nf, 74.72.Bk, 74.72.GrThe high-T c superconductors (HTSC) containing CuO 2 planes are layered materials with anisotropic physical properties. Evidence is now growing that the energy gap in HTSC has "d-wave" symmetry with nodes in the order parameter in certain directions in k space [1,2]. Detailed knowledge of the behavior of the superfluid density and the symmetry of the energy gap are important for understanding various properties of the superconducting state including the pairing mechanism in these materials. One of the best probes of the superfluid density and the energy gap morphology at the Fermi surface is the penetration depth ͑l͒. Many early studies of the temperature ͑T ͒ dependence of l on single crystals, films, and aligned powders of yttrium barium copper oxide (YBCO) gave evidence for non-s-wave pairing, usually in the form of a T 2 behavior for l͑T ͒ at low temperatures rather than exponential dependence expected for s wave. However, this was not widely accepted until the work of Hardy et al. [3] on high quality YBCO crystals which showed a linear temperature dependence in the in-plane penetration depth from 1.3 to 20 K. We have found that in some cases, structural and chemical defects near the surface of YBCO crystallites have significant effects on l at low temperatures and that heat treating the crystallites after grinding in air, or grinding under argon, helped obtain higher quality surfaces and thus intrinsic information from aligned powder composites [4]. Most studies of l have concentrated on YBCO [1,3,5] and Zn doped YBCO [5,6]. Relatively few studies have examined other materials such as La 22x

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“…On the other hand, the quadratic T-dependence of the penetration depth λ(T) (Panagopoulos et al 2001, Pronin et al 2001, Klein et al 2001, as well as the sign reversal of the Hall coefficient near T c (Jin et al 2001a) indicates unconventional superconductivity similar to cuprates. One should also pay more attention to the layered structure of MgB 2 , which may be the key to a higher T c , as in cuprates and borocarbides.…”

Section: Introductionmentioning

confidence: 99%

Review of the superconducting properties of MgB₂

Buzea

Yamashita

2001

Supercond. Sci. Technol.

1,135

672

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This review paper illustrates the main normal and superconducting state properties of magnesium diboride, a material known since the early 1950s but only recently discovered to be superconductive at a remarkably high critical temperature T c = 40 K for a binary compound. What makes MgB 2 so special? Its high T c , simple crystal structure, large coherence lengths, high critical current densities and fields, and transparency of grain boundaries to current promise that MgB 2 will be a good material for both large-scale applications and electronic devices. During the last seven months, MgB 2 has been fabricated in various forms: bulk, single crystals, thin films, tapes and wires. The largest critical current densities, greater than 10 MA cm −2 , and critical fields, 40 T, are achieved for thin films. The anisotropy ratio inferred from upper critical field measurements is yet to be resolved as a wide range of values have been reported, γ = 1.2-9. Also, there is no consensus on the existence of a single anisotropic or double energy gap. One central issue is whether or not MgB 2 represents a new class of superconductors, which is the tip of an iceberg awaiting to be discovered. To date MgB 2 holds the record for the highest T c among simple binary compounds. However, the discovery of superconductivity in MgB 2 revived the interest in non-oxides and initiated a search for superconductivity in related materials; several compounds have since been announced to be superconductive: TaB 2 , BeB 2.75 , C-S composites, and the elemental B under pressure.

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Low Temperature Penetration Depth Measurements in High-T c Superconductors

Cited by 3 publications

References 15 publications

Global trends in the interplane penetration depth of layered superconductors

Global trends in the interplane penetration depth of layered superconductors

Probing the Order Parameter and thec-Axis Coupling of High-TcCuprates by Penetration Depth Measurements

Review of the superconducting properties of MgB₂

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Low Temperature Penetration Depth Measurements in High-T c Superconductors

Cited by 3 publications

References 15 publications

Global trends in the interplane penetration depth of layered superconductors

Global trends in the interplane penetration depth of layered superconductors

Probing the Order Parameter and thec-Axis Coupling of High-TcCuprates by Penetration Depth Measurements

Review of the superconducting properties of MgB2

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Review of the superconducting properties of MgB₂