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Hardy, W. N.; Bonn, D. A.; Morgan, D. C.; Liang, Ruixing; Zhang, Kuan

doi:10.1103/physrevlett.70.3999

Cited by 1,136 publications

(675 citation statements)

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“…First we compare our data with the expectations in unconventional superconductors with nodes in the gap. In clean superconductors with line nodes, thermally excited quasiparticles near the gap nodes give rise to the T -linear temperature dependence of δλ ab (T ) at low temperatures, as observed in YBa 2 Cu 3 O 7−δ crystals with d-wave symmetry [47]. In the d-wave case, δλ ab (T )/λ ab (0) ≈ ln 2 ∆0 k B T is expected [27], where ∆ 0 is the maximum of the energy gap ∆(k).…”

Section: Resultsmentioning

confidence: 99%

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Shibauchi

Hashimoto

Okazaki

et al. 2009

Physica C: Superconductivity

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In this article, we review our recent studies of microwave penetration depth, lower critical fields, and quasiparticle conductivity in the superconducting state of Fe-arsenide superconductors. Highsensitivity microwave surface impedance measurements of the in-plane penetration depth λ ab in single crystals of electron-doped PrFeAsO1−y (y ∼ 0.1) and hole-doped Ba1−xKxFe2As2 (x ≈ 0.55) are presented. In clean crystals of Ba1−xKxFe2As2, as well as in PrFeAsO1−y crystals, the penetration depth shows flat temperature dependence at low temperatures, indicating that the superconducting gap opens all over the Fermi surface. The temperature dependence of superfluid density λ 2 ab (0)/λ 2 ab (T ) in both systems is most consistent with the existence of two different gaps. In Ba1−xKxFe2As2, we find that the superfluid density is sensitive to degrees of disorder inherent in the crystals, implying unconventional impurity effect. We also determine the lower critical field Hc1 in PrFeAsO1−y by using an array of micro-Hall probes. The temperature dependence of Hc1 saturates at low temperatures, fully consistent with the superfluid density determined by microwave measurements. The anisotropy of Hc1 has a weak temperature dependence with smaller values than the anisotropy of upper critical fields at low temperatures, which further supports the multi-gap superconductivity in Fe-arsenide systems. The quasiparticle conductivity shows an enhancement in the superconducting state, which suggests the reduction of quasiparticle scattering rate due to the gap formation below Tc. From these results, we discuss the structure of the superconducting gap in these Fe-arsenides, in comparison with the high-Tc cuprate superconductors.

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Section: Resultsmentioning

confidence: 99%

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Shibauchi

Hashimoto

Okazaki

et al. 2009

Physica C: Superconductivity

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“…Hole-doped high-T c cuprates Early penetration depth measurements in high-T c cuprates claimed either s-wave pairing, probably due to insufficient sensitivity, or 2 T behavior, due to poor quality samples. Microwave measurements on single crystals of 2 7 Y Ba Cu O δ − (YBCO) by Hardy et al [87] were the first to show the linear -T dependence characteristic of line nodes. In Figure 5 we show data for a single crystal of optimally By now, a linear temperature variation in the superfluid density has also has also been observed in penetration depth data, which is sensitive to the gap amplitude at the nodes, ( )…”

Section: Penetration Depth In High-t C Cupratesmentioning

confidence: 99%

“…The pioneering work of Hardy and coworkers demonstrated that high resolution measurements of the London penetration depth could detect the presence of nodal quasiparticles characteristic of a d-wave pairing state [87]. Since that time, a large number of new superconductors have been discovered, many of which exhibit nontrivial departures from BCS behavior.…”

Section: Introductionmentioning

confidence: 99%

Magnetic penetration depth in unconventional superconductors

Prozorov

Giannetta

2006

Supercond. Sci. Technol.

407

438

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Abstract. This topical review summarizes various features of magnetic penetration depth in unconventional superconductors. Precise measurements of the penetration depth as a function of temperature, magnetic field and crystal orientation can provide detailed information about the pairing state. Examples are given of unconventional pairing in hole-and electron-doped cuprates, organic and heavy fermion superconductors. The ability to apply an external magnetic field adds a new dimension to penetration depth measurements. We discuss how field dependent measurements can be used to study surface Andreev bound states, nonlinear Meissner effects, magnetic impurities, magnetic ordering, proximity effects and vortex motion. We also discuss how penetration depth measurements as a function of orientation can be used to explore superconductors with more than one gap and with anisotropic gaps. Details relevant to the analysis of penetration depth data in anisotropic samples are also discussed.Keywords: penetration depth, unconventional superconductivity, pairing symmetry IntroductionThe early suggestion that high temperature superconductors might exhibit unconventional, d-wave pairing, [24,11,154,8] has lead to a wide variety of new experimental probes with sensitivity sufficient to test this hypothesis. The pioneering work of Hardy and coworkers demonstrated that high resolution measurements of the London penetration depth could detect the presence of nodal quasiparticles characteristic of a d-wave pairing state [87]. Since that time, a large number of new superconductors have been discovered, many of which exhibit nontrivial departures from BCS behavior. As we show in this review, penetration depth measurements can be used to examine not only nodal quasiparticles but two-gap superconductivity, anisotropy of the energy gap, Andreev surface states, nonlinear Meissner effect, interplane transport, proximity coupled diamagnetism, vortex matter and the coexistence of magnetism and superconductivity, to name several problems of current interest.

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“…It provides a great deal of information concerning fundamental physics [1], as well as allowing to address essential issues in view of technological applications [2]. The microwave response determined at zero field has allowed to address many points such as the temperature dependence of the superfluid density [3][4][5], and the quasi-particles (QP) properties above and below the superconducting transition [4][5][6]. By applying a static magnetic field H > H c1 , HTCS are driven in the mixed state where the presence of vortices allows for the disclosure of additional physics [5].…”

Section: Introductionmentioning

confidence: 99%