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arXiv · 1907.04033

Two-Gap Superconductivity in CaFe_{0.88}Co_{0.12}AsF Revealed by Temperature Dependence of the Lower Critical Field H_{c1}^c(T)

Teng Wang·Yonghui Ma·Wei Li·Jianan Chu·Lingling Wang·Jiaxin Feng·Hong Xiao·Zhuojun Li·Tao Hu·Xiaosong Liu·Gang Mu
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Abstract

Gap symmetry and structure are crucial issues in understanding the superconducting mechanism of unconventional superconductors. Here we report an in-depth investigation on the out-of-plane lower critical field $H_{c1}^{c}$ of fluorine-based 1111 system superconductor CaFe$_{0.88}$Co$_{0.12}$AsF with $T_c$ = 21 K. A pronounced two-gap feature is revealed by the kink in the temperature dependent $H_{c1}^c(T)$ curve. The magnitudes of the two gaps are determined to be $\Delta_1$ = 0.86 meV and $\Delta_2$ = 4.48 meV, which account for 74% and 26% of the total superfluid density respectively. Our results suggest that the local antiferromagnetic exchange pairing picture is favored compared to the Fermi surface nesting scenario.

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Teng Wang, Yonghui Ma, Wei Li, Jianan Chu, Lingling Wang, Jiaxin Feng, Hong Xiao, Zhuojun Li, Tao Hu, Xiaosong Liu, Gang Mu. 2019-07-09. Two-Gap Superconductivity in CaFe_{0.88}Co_{0.12}AsF Revealed by Temperature Dependence of the Lower Critical Field H_{c1}^c(T). https://doi.org/10.1038/s41535-019-0173-0

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