Superconducting fluctuations in the reversible magnetization of the iron-pnictide<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Ba</mml:mtext></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mtext>K</mml:mtext><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mrow><mml:mtext>Fe</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mtext>As</mml:mtext></mml:mrow>

Salem‐Sugui, S.; Ghivelder, L.; Alvarenga, A. D.; Pimentel, J.L.; Luo, Huiqian; Wang, Zhaosheng; Wen, Hao

doi:10.1103/physrevb.80.014518

Cited by 35 publications

(43 citation statements)

References 44 publications

(91 reference statements)

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“…4(a), were performed with magnetic fields up to 5 T perpendicular to the ab layers, under zero-field-cooled (ZFC) and field-cooled (FC) conditions. As it may be seen in this figure, a rounding effect just below T c (which becomes more prominent upon increasing the applied magnetic field) and a broadening of the reversible region (where the ZFC and FC curves coincide) below T c , are substantial evidences of the fluctuation effects in the critical region, in agreement with recent results 13,14,16 . In this case the background contribution (which is mainly due to the crystal’s normal state) was determined by fitting a curie-like dependence m B ( T ) = a + b T + c / T to the as-measured m ( T ) H data in the temperature range from 25 K to 45 K (solid lines in Fig.…”

Section: Resultssupporting

confidence: 92%

Anisotropy dependence of the fluctuation spectroscopy in the critical and gaussian regimes in superconducting NaFe1−xCo x As single crystals

Ahmad

Choi

Sóñora

et al. 2018

Sci Rep

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We investigate thermal fluctuations in terms of diamagnetism and magnetotransport in superconducting NaFe1−xCoxAs single crystals with different doping levels. Results show that in the case of optimal doped and lightly overdoped (x = 0.03, 0.05) crystals the analysis in the critical as well as in the Gaussian fluctuation regions is consistent with the Ginzburg-Landau 3D fluctuation theory. However, in the case of strongly overdoped samples (x ≥ 0.07) the Ullah-Dorsey scaling of the fluctuation induced magnetoconductivity in the critical region confirms that thermal fluctuations exhibit a 3D anisotropic nature only in a narrow temperature region around Tc(H). This is consistent with the fact that in these samples the fluctuation effects in the Gaussian region above Tc may be described by the Lawrence-Doniach approach. Our results indicate that the anisotropy of these materials increases significantly with the doping level.

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Section: Resultssupporting

confidence: 92%

Anisotropy dependence of the fluctuation spectroscopy in the critical and gaussian regimes in superconducting NaFe1−xCo x As single crystals

Ahmad

Choi

Sóñora

et al. 2018

Sci Rep

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“…Regarding the magnetization fluctuations, we point out that a 3D fluctuation magnetization of the lowest Landau level (LLL) type has been observed in Ba 1−x K x Fe 2 As 2 single crystals in a temperature window above the magnetic field-dependent critical temperature [23]. We note that these results have been obtained for two K contents: x = 0.28 and x = 0.25.…”

Section: Introductionmentioning

confidence: 59%

Paraconductivity of the K-doped SrFe₂As₂superconductor

Marra

Nigro

et al. 2012

New J. Phys.

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Paraconductivity of the optimally K-doped SrFe2As2 superconductor is investigated within existing fluctuation mechanisms. The in-plane excess conductivity has been measured in high quality single crystals, with a sharp superconducting transition at Tc=35.5 K and a transition width less than 0.3 K. The data have been also acquired in external magnetic field up to 14 T. We show that the fluctuation conductivity data in zero field and for temperatures close to Tc, can be explained within a three-dimensional Lawrence-Doniach theory, with a negligible Maki-Thompson contribution. In the presence of the magnetic field, it is shown that paraconductivity obeys the three-dimensional Ullah-Dorsey scaling law, above 2 T and for H c. The estimated upper critical field and the coherence length nicely agree with the available experimental data.

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“…These results are further supported by directional point-contact Andreev-reflection spectroscopy 29 and microwave surface impedance 30 data which suggest fully-, and perhaps multiply-, gapped superconductivity. However, the possibility for a nodal gap has not been completely ruled out: measurements of reversible magnetization 31 platelets and the samples used in these measurements were carefully selected to be the best single crystals available. The sample surfaces are known to degrade from prolonged exposure to ambient atmosphere.…”

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confidence: 99%

Precision microwave electrodynamic measurements of K- and Co-dopedBaFe2As2

et al. 2010

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We have studied the microwave electrodynamics of single crystal iron-based superconductors Ba0.72K0.28Fe2As2 (hole-doped, Tc ≈ 30 K) and Ba(Fe0.95Co0.05)2As2 (electron-doped, Tc ≈20 K), by cavity perturbation and broadband spectroscopy. SQUID magnetometry was used to confirm the quality and homogeneity of the samples under study. Through cavity perturbation techniques, the temperature dependence of the in-plane London penetration depth ∆λ(T ), and therefore the superfluid phase stiffness λ 2 (0)/λ 2 (T ) was measured. Down to 0.4 K, the data do not show the exponential saturation at low temperatures expected from a singly-, fully-gapped superconductor. Rather, both the electron-and the hole-doped systems seem to be best described by a power law behavior, with λ 2 (0)/λ 2 (T ) ∼ T n and n ≈ 2.5. In the three samples we studied, a weak feature near the sensitivity limit of our measurements appears near T /Tc = 0.04, hinting at a corresponding low energy feature in the superconducting density of states. The data can also be relatively well-described by a simple two-gap s-wave model of the order parameter, but this yields parameters which seem unrealistic and dependent on the fit range. Broadband surface resistance measurements reveal a sample dependent residual loss whose origin is unclear. The data from the Ba0.72K0.28Fe2As2 samples can be made to scale as ω 2 if the extrinsic loss is treated as an additive component, indicating large scattering rates. Finally, the temperature dependence of the surface resistance at 13 GHz obeys a power law very similar to those observed for ∆λ(T ).

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Superconducting fluctuations in the reversible magnetization of the iron-pnictideBa1−xKxFe2As

Cited by 35 publications

References 44 publications

Anisotropy dependence of the fluctuation spectroscopy in the critical and gaussian regimes in superconducting NaFe1−xCo x As single crystals

Anisotropy dependence of the fluctuation spectroscopy in the critical and gaussian regimes in superconducting NaFe1−xCo x As single crystals

Paraconductivity of the K-doped SrFe₂As₂superconductor

Precision microwave electrodynamic measurements of K- and Co-dopedBaFe2As2

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Superconducting fluctuations in the reversible magnetization of the iron-pnictideBa1−xKxFe2As

Cited by 35 publications

References 44 publications

Anisotropy dependence of the fluctuation spectroscopy in the critical and gaussian regimes in superconducting NaFe1−xCo x As single crystals

Anisotropy dependence of the fluctuation spectroscopy in the critical and gaussian regimes in superconducting NaFe1−xCo x As single crystals

Paraconductivity of the K-doped SrFe2As2superconductor

Precision microwave electrodynamic measurements of K- and Co-dopedBaFe2As2

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Product

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Paraconductivity of the K-doped SrFe₂As₂superconductor