Anisotropic superconducting properties of single-crystallineFeSe0.5Te0.5

Abstract

Iron-chalcogenide single crystals with the nominal composition FeSe0.5Te0.5 and a transition temperature of Tc14.6 K were synthesized by the Bridgman method. The structural and anisotropic superconducting properties of those crystals were investigated by means of single crystal x-ray and neutron powder diffraction, superconducting quantum interference device and torque magnetometry, and muon-spin rotation (SR). Room temperature neutron powder diffraction reveals that 95% of the crystal volume is of the same tetragonal structure as PbO. The structure refinement yields a stoichiometry of Fe1.045Se0.406Te0.594. Additionally, a minor hexagonal Fe7Se8 impurity phase was identified. The magnetic penetration depth at zero temperature obtained by means of SR was found to be ab(0)=491 (8) PREPRINT (April 7, 2010) Anisotropic Iron-chalcogenide single crystals with the nominal composition FeSe0.5Te0.5 and a transition temperature of Tc 14.6 K were synthesized by the Bridgman method. The structural and anisotropic superconducting properties of those crystals were investigated by means of single crystal X-ray and neutron powder diffraction, SQUID and torque magnetometry, and muon-spin rotation. Room temperature neutron powder diffraction reveals that 95% of the crystal volume is of the same tetragonal structure as PbO. The structure refinement yields a stoichiometry of Fe1.045Se0.406Te0.594. Additionally, a minor hexagonal Fe7Se8 impurity phase was identified. The magnetic penetration depth λ at zero temperature was found to be λ ab (0) = 491(8) nm in the ab-plane and λc(0) = 1320(14) nm along the c-axis. The zero-temperature value of the superfluid density ρs(0) ∝ λ −2 (0) obeys the empirical Uemura relation observed for various unconventional superconductors, including cuprates and ironpnictides. The temperature dependences of both λ ab and λc are well described by a two-gap s+s-wave model with the zero-temperature gap values of ∆S(0) = 0.51(3) meV and ∆L(0) = 2.61(9) meV for the small and the large gap, respectively. The magnetic penetration depth anisotropy parameter γ λ (T ) = λc(T )/λ ab (T ) increases with decreasing temperature, in agreement with γ λ (T ) observed in the iron-pnictide superconductors.superconducting properties of single-crystalline FeSe 0.5 Te 0.

Precision global measurements of London penetration depth in FeTe0.58Se0.42

“…The zero temperature values of the energy gaps ∆ I (0) and ∆ II (0) are 2.5 meV (∆ I (0)/k B T c = 1.93) and 1.1 meV (∆ II (0)/k B T c = 0.9), respectively. From the previous measurements, such as µSR 32,33 and penetration depth, 24 two isotropic gaps were reported with gap values similar to our results. µSR studies in FeSe 0.5 Te 0.5 [32 and 33] revealed two gaps of ∆ large ∼ 2.6 meV and ∆ small ∼ 0.5-0.87 meV, and the penetration depth study 24 also showed that ∆ large ∼ 2.1 meV and ∆ s ∼ 1.2 meV.…”

High-pressure flux growth, structural, and superconducting properties ofLnFeAsO (Ln=Pr, Nd, Sm) single cryst

“…We estimate from the crystal dimensions the approximate demagnetization factors anisotropy at low temperatures is estimated to be ∼ 2.8, which is in good agreement with previous reports [38,39]. Since according to [40] ( 1) it is possible to estimate the penetration depths being equal to λ ab ≈ 250 nm and λ c ≈ 970 nm, invoking the coherence lengths of ξ ab ≈ 4 nm and ξ c ≈ 0.8 nm estimated by the resistivity measurements discussed below. indicate an increase in the effectiveness of pinning centers giving rise to a "peak effect".…”

Muon-spin rotation measurements of the magnetic penetration depth in the iron-based superconductor Ba1−xRbxFeGuguchia1, Shermadini2, Amato3 et al. 2011Phys. Rev. BSelf Cite237400View full textAdd to dashboardCite

“…A two-gap scenario is in line with the generally accepted view of multi-gap superconductivity in Fe-based HTS. 5,6,8,[27][28][29] The magnitudes of the large and the small gap for Ba 1−x Rb x Fe 2 As 2 (x = 0.3, 0.35, 0.4) (see Table I) are in good agreement with the results of a previous report. 5 There it was pointed out that most Fe-based HTS's exhibit two-gap superconducting behavior, characterized by a large gap with 2∆/k B T c = 7(2) and a small one with 2.5(1.5).…”