Temperature dependence of the superconducting energy gaps in Ca
9.35La
0.65(Pt
3As
8)(Fe
2As
2)
5 single crystal.
Sci Rep 2018;
8:8648. [PMID:
29872157 PMCID:
PMC5988743 DOI:
10.1038/s41598-018-24940-9]
[Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 04/10/2018] [Indexed: 12/01/2022] Open
Abstract
We measured the optical reflectivity R(ω) for an underdoped (Ca0.935La0.065)10(Pt3As8)(Fe2As2)5 single crystal and obtained the optical conductivity \documentclass[12pt]{minimal}
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\begin{document}$${\sigma }_{1}(\omega )$$\end{document}σ1(ω) using the K-K transformation. The normal state \documentclass[12pt]{minimal}
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\begin{document}$${\sigma }_{1}(\omega )$$\end{document}σ1(ω) at 30 K is well fitted by a Drude-Lorentz model with two Drude components (ωp1 = 1446 cm−1 and ωp2 = 6322 cm−1) and seven Lorentz components. Relative reflectometry was used to accurately determine the temperature dependence of the superconducting gap at various temperatures below Tc. The results clearly show the opening of a superconducting gap with a weaker second gap structure; the magnitudes for the gaps are estimated from the generalized Mattis-Bardeen model to be Δ1 = 30 and Δ2 = 50 cm−1, respectively, at T = 8 K, which both decrease with increasing temperature. The temperature dependence of the gaps was not consistent with one-band BCS theory but was well described by a two-band (hence, two gap) BCS model with interband interactions. The temperature dependence of the superfluid density is flat at low temperatures, indicating an s-wave full-gap superconducting state.
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