Lower critical fields of superconducting<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>PrFeAsO</mml:mtext></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>y</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>single crystals

Okazaki, Renji; Kończykowski, M.; Beek, C.J. van der; Kato, Terumasa; Hashimoto, K.; Shimozawa, Masaaki; Shishido, Hiroaki; Yamashita, Minoru; Ishikado, M.; Kitô, Hijiri; Iyo, A.; Eisaki, H.; Shamoto, S.; Shibauchi, T.; Matsuda, Yuji

doi:10.1103/physrevb.79.064520

Cited by 65 publications

(60 citation statements)

References 42 publications

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“…31,32) This again supports that Sc 5 Ir 4 Si 10 is not a two-gap superconductor. The value of γ is roughly 0.45, reflecting the weakly one-dimensional Fermi surface, which is in consistent with the chainlike structure along the c-axis and the quasi-one-dimensional electronic band structure.…”

Section: )supporting

confidence: 52%

Specific Heat and Upper Critical Field of Sc₅Ir₄Si₁₀Superconductor

Sun

Ding

et al. 2013

J. Phys. Soc. Jpn.

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Temperature and magnetic field dependent specific heat of textured Sc 5 Ir 4 Si 10 superconductor was investigated in detail. Based on the fitting of zero-field electronic specific heat by different gap structures as well as the discussion on field-induced specific heat coefficient, Sc 5 Ir 4 Si 10 is proved to be an anisotropic s-wave superconductor with a gap anisotropy, min max / Δ Δ , of 0.53. The anisotropy of upper critical field suggests the weakly one-dimensional Fermi surface, and the value is consistent with the gap anisotropy result obtained from the specific heat data.

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Section: )supporting

confidence: 52%

Specific Heat and Upper Critical Field of Sc₅Ir₄Si₁₀Superconductor

Sun

Ding

et al. 2013

J. Phys. Soc. Jpn.

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“…even smaller than our first penetration field values (∼ 55 G). Note that strong bulk pinning could lead to an overestimation of H p , if measured in the center of the sample (see for instance [34]) but we checked that very similar H p values are obtained for several probe positions by placing the sample on an array of 11 miniature (10 × 10 µm 2 ) probes : as shown in the left inset of Fig.2, the field distribution clearly presents the V − shape profile characteristic of a strong bulk pinning. Even though those profiles confirm the good homogeneity of the sample, one can not exclude the presence of a strong disorder at the surface of the samples leading to a surface penetration field much larger than the bulk value.…”

Section: Hc1mentioning

confidence: 70%

s-wave superconductivity probed by measuring magnetic penetration depth and lower critical field ofMgCNi3single crystals

et al. 2009

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The magnetic penetration depth λ has been measured in MgCNi3 single crystals using both a high precision Tunnel Diode Oscillator technique (TDO) and Hall probe magnetization (HPM). In striking contrast to previous measurements in powders, δλ(T) deduced from TDO measurements increases exponentially at low temperature, clearly showing that the superconducting gap is fully open over the whole Fermi surface. An absolute value at zero temperature λ(0) =230 nm is found from the lower critical field measured by HPM. We also discuss the observed difference of the superfluid density deduced from both techniques. A possible explanation could be due to a systematic decrease of the critical temperature at the sample surface.PACS numbers: 74.25. Nf, 74.25.Op, 74.70.Dd The interplay between magnetism and superconductivity is currently a subject of great interest. In the UGe 2 and URhGe uranium compounds, for instance, a long range ferromagnetic ordered phase coexists with the superconducting phase and a mechanism of spin fluctuations (SF) could be at the origin of the Cooper pair formation [1, 2]. The recent discovery of high temperature superconductivity in oxypnictides also rapidly became the topic of a tremendous number of both experimental and theoretical works. The parent undoped LnOFeAs (where Ln=La,Sm,...) compound is here close to itinerant magnetism due to the presence of a high density of Fe d states at the Fermi level [3], leading to competing ferromagnetic and antiferromagnetic fluctuations. Similarly in the cubic (anti-)perovskite MgCNi 3 compound [4], the presence of a strong Van Hove singularity in the density of Ni states slightly below the Fermi level also leads to strong ferromagnetic fluctuations [5][6][7][8][9]. These two systems have also a Fermi surface composed of both electron and hole pockets (3D sheets in MgCNi 3 as compared to quasi-cylindrical sheets in oxypnictides).Despite these striking similarities in their electronic and magnetic properties, spin fluctuations lead to very different effects in those systems. On the one hand, ab-initio calculations rapidly showed that the electronphonon coupling constant (λ e−ph ∼ 0.2) is far too low to account for the high critical temperatures observed in oxypnictides (up to ∼ 55 K) and an unconventional mechanism mediated by the SF associated with a sign reversal of the (s-wave) order parameter between electrons and holes sheets of the Fermi surface has been proposed [10]. On the other hand, it has been suggested that the narrow van Hove singularity could be responsible for a nearly unstable phonon mode in MgCNi 3 inducing a large, although reduced by SF, λ e−ph [11,12] in agreement with experiments which yield an average electronphonon coupling constant in the order of 1.7 [11,13,14]. The interplay between electron-phonon coupling and SF is further emphasized in this system by the existence of a large isotopic effect [15] which has been suggested to be enhanced by the strong SF [16].In this context, the nature of the superconducting order parameter rapidl...

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“…By using a sensitive superconducting cavity resonator, we can measure both real and imaginary parts of Z s pricesely in tiny single crystals, from which we can extract the in-plane penetration depth λ ab (T ) as well as quasiparticle conductivity σ 1 (T ) that yields information on the quasiparticle dynamics. We also measure H c1 (T ) in PrFeAsO 1−y crystals by using an unambiguous method to avoid the difficulty associated with pinning [37]. We directly determine the field H p at which first flux penetration occurs from the edge of the crystal by measuring the magnetic induction just inside and outside the edge of the single crystals, with the use of a miniature Hall-sensor array.…”

Section: Introductionmentioning

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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Lower critical fields of superconductingPrFeAsO1−ysingle crystals

Cited by 65 publications

References 42 publications

Specific Heat and Upper Critical Field of Sc₅Ir₄Si₁₀Superconductor

Specific Heat and Upper Critical Field of Sc₅Ir₄Si₁₀Superconductor

s-wave superconductivity probed by measuring magnetic penetration depth and lower critical field ofMgCNi3single crystals

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

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Lower critical fields of superconductingPrFeAsO1−ysingle crystals

Cited by 65 publications

References 42 publications

Specific Heat and Upper Critical Field of Sc5Ir4Si10Superconductor

Specific Heat and Upper Critical Field of Sc5Ir4Si10Superconductor

s-wave superconductivity probed by measuring magnetic penetration depth and lower critical field ofMgCNi3single crystals

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

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Specific Heat and Upper Critical Field of Sc₅Ir₄Si₁₀Superconductor

Specific Heat and Upper Critical Field of Sc₅Ir₄Si₁₀Superconductor