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Anisotropic superconducting properties of single-crystalline FeSe_{0.5}Te_{0.5}


Bendele, M; Weyeneth, S; Puzniak, R; Maisuradze, A; Pomjakushina, E; Conder, K; Pomjakushin, V; Luetkens, H; Katrych, S; Wisniewski, A; Khasanov, R; Keller, H (2010). Anisotropic superconducting properties of single-crystalline FeSe_{0.5}Te_{0.5}. Physical Review. B, Condensed Matter and Materials Physics, 81(22):224520 .

Abstract

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, superconducting quantum interference device and torque magnetometry, and muon-spin rotation (μSR). 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 obtained by means of μSR was found to be λab(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 iron pnictides. The temperature dependences of both λab and λc are well described by a two-gap s+s-wave model with the zero-temperature gap values of ΔS(0)=0.51(3) meV and ΔL(0)=2.61(9) meV for the small and the large gap, respectively. The magnetic penetration depth anisotropy parameter γλ(T)=λc(T)/λab(T) increases with decreasing temperature, in agreement with γλ(T) observed in the iron-pnictide superconductors.

© 2010 The American Physical Society

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, superconducting quantum interference device and torque magnetometry, and muon-spin rotation (μSR). 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 obtained by means of μSR was found to be λab(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 iron pnictides. The temperature dependences of both λab and λc are well described by a two-gap s+s-wave model with the zero-temperature gap values of ΔS(0)=0.51(3) meV and ΔL(0)=2.61(9) meV for the small and the large gap, respectively. The magnetic penetration depth anisotropy parameter γλ(T)=λc(T)/λab(T) increases with decreasing temperature, in agreement with γλ(T) observed in the iron-pnictide superconductors.

© 2010 The American Physical Society

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Language:English
Date:2010
Deposited On:13 Feb 2011 14:46
Last Modified:05 Apr 2016 14:45
Publisher:American Physical Society
ISSN:1098-0121
Publisher DOI:https://doi.org/10.1103/PhysRevB.81.224520
Related URLs:http://arxiv.org/abs/1004.0812
Permanent URL: https://doi.org/10.5167/uzh-45334

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