Superconducting Gap Structures and Interband Fluctuations in Electron-Doped Pnictide Ca0.85La0.15Fe2As2 Single Crystals

International Journal of Physics | Vol. 12, No. 8, August 2021 | pp. 57–64

DOI: 10.46882/2021/IJP/000136

Research Article

Title: Superconducting Gap Structures and Interband Fluctuations in Electron-Doped Pnictide Ca0.85La0.15Fe2As2 Single Crystals

Names of Authors: I. R. Sokolov¹, A. A. Menshikov²

Authors’ Affiliations:
¹ Kapitza Institute for Physical Problems, Russian Academy of Sciences, Moscow, Russia
² Institute for Solid State Physics, Russian Academy of Sciences, Chernogolovka, Russia

Abstract: Identifying the exact pairing symmetries of iron-based pnictide materials is a principal research objective for expanding high-temperature superconducting models and electronic layouts. We synthesized high-quality single crystals of electron-doped Ca0.85La0.15Fe2As2 utilizing a high-pressure flux growth methodology executed at 4.8 GPa. The internal superconducting gap structures and localized 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 = 32.5 K with an narrow magnetic susceptibility transition width of ΔT = 0.3 K. The temperature dependence of the London penetration depth shows a distinct exponential behavior at low thresholds (T less than 0.3 Tc), which rules out the presence of line nodes in the order parameter. The photoemission spectra mapped out two separate, fully gapped isotropic superconducting bands across the Fermi surface. The larger gap value was measured at Δ1 = 8.4 meV on the inner hole-like sheet, while the smaller gap was found at Δ2 = 4.2 meV on the outer electron-like sheets. This gap configuration yields a strong-coupling ratio of 2Δ1/kBTc = 6.0, confirming an s± pairing symmetry model driven by interband spin fluctuations.

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

Manuscript Timeline: Received: April 05, 2021; Revised: June 01, 2021; Accepted: June 28, 2021; Published: August 16, 2021

Citation: Sokolov, I. R., & Menshikov, A. A. (2021). Superconducting Gap Structures and Interband Fluctuations in Electron-Doped Pnictide Ca0.85La0.15Fe2As2 Single Crystals. International Journal of Physics, 12(8), 57–64.

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