Two-gap superconducting properties of alkaline-earth intercalated Ax(NH3)Fe2Se2 (A = Ba or Sr)

Yung Yuan Hsu, Yu Bo Li, Shou Ting Jian, Gu Kuei Li, Ming Cheng Yang

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Abstract

Superconducting properties were studied on high quality superconductors Bax(NH3)Fe2Se2 (Tc= 39 K) and Srx(NH3)Fe2Se2 (Tc = 44 K) prepared by intercalating Ba/Sr atoms into tetragonal β-FeSe by liquid ammonia. The elongated c-axis and almost unchanged a-axis of Bax(NH3)Fe2Se2, compared with β-FeSe, suggests an unchanged intra- Fe2Se2-layer structure and the Tc enhancement is due to a 3D to 2D-like Fermi surface transformation. The superconducting coherent lengths (0), the Ginzburg-Landau parameters κ and penetration depths (0) obtained from the extrapolated lower and upper critical fields Bc1 (0) and Bc2 (0) indicate that both compounds are typical type-II superconductors. The temperature dependence of 1/l2(T) of Bax(NH3)Fe2Se2 deduced from the low-field magnetic susceptibility shows a twogap s-wave behavior with superconducting gaps of δ1 = 6.47 meV and δ2= 1.06 meV.

Original languageEnglish
Article number035005
JournalSuperconductor Science and Technology
Volume29
Issue number3
DOIs
Publication statusPublished - 2016 Jan 22
Externally publishedYes

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Keywords

  • alkaline-earth intercalated FeSe
  • Ginzburg-Landau parameter
  • iron chacogenide
  • penetration depth
  • two-gap s-wave superconductor

ASJC Scopus subject areas

  • Ceramics and Composites
  • Condensed Matter Physics
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry

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