Superconducting Gap Structure and Spin Fluctuations in Electron-Doped Pnictide LaFeAsO0.85F0.15 Single Crystals

International Journal of Physics | Vol. 6, No. 11, November 2015 | pp. 81–88

DOI: 10.46882/2015/IJP/000067

Research Article

Title: Superconducting Gap Structure and Spin Fluctuations in Electron-Doped Pnictide LaFeAsO0.85F0.15 Single Crystals

Names of Authors: I. R. Sokolov¹, B. J. Holford²

Authors’ Affiliations: ¹Kapitza Institute for Physical Problems, Russian Academy of Sciences, Moscow, Russia; ²Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK

Abstract: Uncovering the exact pairing symmetry of iron-based pnictide superconductors remains a primary challenge in modern condensed matter physics. We synthesized high-quality single crystals of electron-doped LaFeAsO0.85F0.15 utilizing a high-pressure flux growth methodology at 4.5 GPa. 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 = 26.5 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 bands. The larger gap value was measured at Δ1 = 7.2 meV on the inner hole-like Fermi surface sheet, while the smaller gap was found at Δ2 = 3.6 meV on the electron-like sheets. This gap configuration yields a strong-coupling ratio of 2Δ1/kBTc = 6.3, 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: July 12, 2015; Revised: September 04, 2015; Accepted: September 22, 2015; Published: November 12, 2015

Citation: Sokolov, I. R., & Holford, B. J. (2015). Superconducting Gap Structure and Spin Fluctuations in Electron-Doped Pnictide LaFeAsO0.85F0.15 Single Crystals. International Journal of Physics, 6(11), 81–88.

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