International Journal of Physics

International Journal of Physics | Vol. 10, No. 9, September 2019 | pp. 65–72

DOI: 10.46882/2019/IJP/000113

Research Article

Title: Superconducting Gap Profiles and Interband Spin Fluctuations in Electron-Doped Pnictide CaFe2As2 Crystals

Names of Authors: I. R. Sokolov¹, V. I. Morozov²

Authors’ Affiliations: ¹Kapitza Institute for Physical Problems, Russian Academy of Sciences, Moscow, Russia; ²Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Russia

Abstract: Establishing the exact pairing symmetries of iron-based pnictide superconductors remains a primary objective within modern solid-state and condensed matter physics. We synthesized high-quality single crystals of electron-doped CaFe2As2 using a specialized self-flux crystal growth routine under pressure. The internal superconducting gap profiles and spin fluctuations were evaluated using high-resolution angle-resolved photoemission spectroscopy and low-temperature London penetration depth tracking. The single crystals displayed a sharp superconducting transition at Tc = 26.0 K with an exceptionally narrow magnetic susceptibility transition width of ΔT = 0.3 K. The temperature dependence of the London penetration depth exhibits an exponential profile at low operational parameters (T less than 0.3 Tc), ruling out the existence of line nodes across the order parameter. The photoemission mapping revealed two distinct, fully gapped isotropic superconducting bands. The large gap magnitude was measured at Δ1 = 7.1 meV on the inner hole-like Fermi surface sheet, while the lower gap registered at Δ2 = 3.5 meV on the outer electron-like sheets. This structure yields a strong-coupling index of 2Δ1/kBTc = 6.3, verifying strong-coupling pairing driven by interband spin fluctuations.

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

Manuscript Timeline: Received: May 14, 2019; Revised: July 08, 2019; Accepted: August 03, 2019; Published: September 10, 2019

Citation: Sokolov, I. R., & Morozov, V. I. (2019). Superconducting Gap Profiles and Interband Spin Fluctuations in Electron-Doped Pnictide CaFe2As2 Crystals. International Journal of Physics, 10(9), 65–72.

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