Superconducting Gap Structure and Spin Fluctuations in Electron-Doped Pnictide Ba(Fe0.92Co0.08)2As2 Single Crystals

International Journal of Physics | Vol. 4, No. 12, December 2013 | pp. 89–96

DOI: 10.46882/2013/IJP/000044

Research Article

Title: Superconducting Gap Structure and Spin Fluctuations in Electron-Doped Pnictide Ba(Fe0.92Co0.08)2As2 Single Crystals

Names of Authors: I. R. Sokolov¹, E. C. Sterling²

Authors’ Affiliations: ¹Kapitza Institute for Physical Problems, Russian Academy of Sciences, Moscow 119334, Russia; ²Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom

Abstract: Uncovering the exact pairing symmetry of iron-based superconductors remains a critical challenge in modern condensed matter physics. We synthesized high-quality single crystals of electron-doped Ba(Fe0.92Co0.08)2As2 utilizing a self-flux method. The superconducting gap structure and spin fluctuations were evaluated through high-resolution angle-resolved photoemission spectroscopy and low-temperature London penetration depth measurements. The single crystals exhibited a sharp superconducting transition at Tc = 25.4 K with a magnetic susceptibility transition width of ΔT = 0.3 K. The temperature dependence of the London penetration depth shows an exponential behavior at low temperatures (T less than 0.3 Tc), which rules out the presence of line nodes in the order parameter. The photoemission spectra revealed two distinct, fully gapped isotropic superconducting superconducting bands. The larger gap value was measured at Δ1 = 6.8 meV on the inner hole-like Fermi surface sheet, while the smaller gap was found at Δ2 = 3.4 meV on the electron-like sheets. This gap configuration yields a strong-coupling ratio of 2Δ1/kBTc = 6.2, indicating strong-coupling superconductivity. These experimental results align with the s± pairing symmetry model driven by interband spin fluctuations.

Keywords: Iron-based superconductors; gap structure; angle-resolved photoemission spectroscopy; London penetration depth; pairing symmetry; spin fluctuations

Manuscript Timeline: Received: August 18, 2013; Revised: October 10, 2013; Accepted: November 02, 2013; Published: December 16, 2013

Citation: Sokolov, I. R., & Sterling, E. C. (2013). Superconducting Gap Structure and Spin Fluctuations in Electron-Doped Pnictide Ba(Fe0.92Co0.08)2As2 Single Crystals. International Journal of Physics, 4(12), 89–96.

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