Temperature dependence of lower critical field<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>H</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mi>T</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math>shows nodeless superconductivity in FeSe

Abdel-Hafiez, M.; Ge, Jun‐Yi; Vasiliev, A. N.; Чареев, Д. А.; Vondel, J. Van de; Moshchalkov, Victor; Silhanek, Alejandro

doi:10.1103/physrevb.88.174512

Cited by 98 publications

(92 citation statements)

References 61 publications

(81 reference statements)

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“…β-FeSe single crystals present T c = 8.4(1) K, penetration depth λ ab (0) ∼ 445 nm [15], coherence length ξ ab (0) ∼ 4.4 nm and a temperature dependent anisotropy, which satisfies γ(T → T c ) ∼ 3 and γ(T → 0) ∼ 1 [16]. The intrinsic thermal fluctuations can be parameterized by the Ginzburg number, and the theoretical depairing critical current density and cuprates (∼ 10 −2 ).…”

Section: Introductionmentioning

confidence: 99%

Vortex dynamics inβ-FeSe single crystals: effects of proton irradiation and small inhomogeneous stress

Amigó¹,

Haberkorn²,

Pérez³

et al. 2017

Supercond. Sci. Technol.

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Abstract.We report on the critical current density Jc and the vortex dynamics of pristine and 3 MeV proton irradiated (cumulative dose equal to 2×10 16 cm −2 ) β-FeSe single crystals.We also analyze a remarkable dependence of the superconducting critical temperature Tc, Jc and the flux creep rate S on the sample mounting method. Free-standing crystals present Tc=8.4(1)K, which increases to 10.5(1)K when they are fixed to the sample holder by embedding them with GE-7031 varnish. On the other hand, the irradiation has a marginal effect on Tc. The pinning scenario can be ascribed to twin boundaries and random point defects. We find that the main effect of irradiation is to increase the density of random point defects, while the embedding mainly reduces the density of twin boundaries. Pristine and irradiated crystals present two outstanding features in the temperature dependence of the flux creep rate: S(T ) presents large values at low temperatures, which can be attributed to small pinning energies, and a plateau at intermediate temperatures, which can be associated with glassy relaxation. From Maley analysis, we observe that the characteristic glassy exponent µ changes from ∼ 1.7 to 1.35-1.4 after proton irradiation.

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Section: Introductionmentioning

confidence: 99%

Vortex dynamics inβ-FeSe single crystals: effects of proton irradiation and small inhomogeneous stress

Amigó¹,

Haberkorn²,

Pérez³

et al. 2017

Supercond. Sci. Technol.

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“…We used a well-known approach to determine lower critical field by measuring the magnetization M as a function of H and then identified the deviation of the linear Meissner response which would correspond to the vortex penetration. Here we assume that no surface barriers are present, thus assuring that H c1 coincides with vortex penetration [29,30].…”

Section: 2 Lower Critical Field Measurementsmentioning

confidence: 99%

Direct evidence of two superconducting gaps in FeSe0.5Te0.5: SnS-Andreev spectroscopy and the lower critical field

et al. 2016

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We present direct measurements of the superconducting order parameter in nearly optimal FeSe0.5Te0.5 single crystals with critical temperature TC ≈ 14 K. Using intrinsic multiple Andreev reflection effect (IMARE) spectroscopy and measurements of lower critical field, we directly determined two superconducting gaps, ∆L ≈ 3.3 − 3.4 meV and ∆S ≈ 1 meV, and their temperature dependences. We show that a two-band model fits well the experimental data. The estimated electron-boson coupling constants indicate a strong intraband and a moderate interband interaction.

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“…For systems with both hole and electron Fermi surfaces, such as optimally doped Ba 1−x K x Fe 2 As 2 [11], Ba(Fe 1−x Co x ) 2 As 2 [15], NaFe 1−x Co x As [19], and Fe(Se, Te) [20], the gaps measured by low-temperature specific heat fit well to the predictions of two nodeless SC gaps. The temperature dependence of the lower critical field in LiFeAs [26], Ba 0.6 K 0.4 Fe 2 As 2 [27], FeSe [28], and Ca 0.32 Na 0.68 Fe 2 As 2 [9] has supported the existence of two s-wave-like gaps. The possibility of nodes along the c axis in the superconducting gap has been reported in NdFeAsO 0.82 F 0.…”

Section: Introductionmentioning

confidence: 99%

Nodeless superconductivity in the presence of spin-density wave in pnictide superconductors: The case ofBaFe2−xNixAs2

Abdel-Hafiez

Zhang

et al. 2015

Phys. Rev. B

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The characteristics of Fe-based superconductors are manifested in their electronic, magnetic properties, and pairing symmetry of the Cooper pair, but the latter remain to be explored. Usually in these materials, superconductivity coexists and competes with magnetic order, giving unconventional pairing mechanisms. We report on the results of the bulk magnetization measurements in the superconducting state and the low-temperature specific heat down to 0.4 K for BaFe 2−x Ni x As 2 single crystals. The electronic specific heat displays a pronounced anomaly at the superconducting transition temperature and a small residual part at low temperatures in the superconducting state. The normal-state Sommerfeld coefficient increases with Ni doping for x = 0.092, 0.096, and 0.10, which illustrates the competition between magnetism and superconductivity. Our analysis of the temperature dependence of the superconducting-state specific heat and the London penetration depth provides strong evidence for a two-band s-wave order parameter. Further, the data of the London penetration depth calculated from the lower critical field follow an exponential temperature dependence, characteristic of a fully gapped superconductor. These observations clearly show that the superconducting gap in the nearly optimally doped compounds is nodeless.

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Temperature dependence of lower critical fieldHc1(T)shows nodeless superconductivity in FeSe

Cited by 98 publications

References 61 publications

Vortex dynamics inβ-FeSe single crystals: effects of proton irradiation and small inhomogeneous stress

Vortex dynamics inβ-FeSe single crystals: effects of proton irradiation and small inhomogeneous stress

Direct evidence of two superconducting gaps in FeSe0.5Te0.5: SnS-Andreev spectroscopy and the lower critical field

Nodeless superconductivity in the presence of spin-density wave in pnictide superconductors: The case ofBaFe2−xNixAs2

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