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arXiv 1708.01006cond-mat.supr-con
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新型铁基超导体CaKFe4As4的自旋共振

Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4

K. Iida, M. Ishikado, Y. Nagai, H. Yoshida, A. D. Christianson, N. Murai, K. Kawashima, Y. Yoshida, H. Eisaki, A. Iyo

摘要:

采用非弹性中子散射(INS)测量和无规相近似(RPA)计算相结合的方法,研究了新型铁基超导体CaKFe $_4$ As $_4$的动态自旋磁化率.粉末INS测量表明,在$Q_\text{res}=1.17(1)$ ~ $\textÅ^{-1}$处的自旋共振,对应于四元数表示的$(π,π)$嵌套波矢,在$T_\text{c}$以下演化。自旋共振$E_\text{res}=12.5$ ~meV的特征能量小于超导能隙尺寸($2Δ$)的两倍。自旋共振动力学磁化率的宽能量特征可以通过RPA计算来解释,其中考虑了不同费米表面上的不同超导能隙。我们的INS和PRA研究表明,CaKFe $_4$ As $_4$的超导配对性质是$s_\pm$对称性。

英文摘要:

The dynamical spin susceptibility in the new-structure-type iron-based superconductor CaKFe$_4$As$_4$ was investigated by using a combination of inelastic neutron scattering (INS) measurements and random phase approximation (RPA) calculations. Powder INS measurements show that the spin resonance at $Q_\text{res}=1.17(1)$~$\textÅ^{-1}$, corresponding to the $(π,π)$ nesting wave vector in tetragonal notation, evolves below $T_\text{c}$. The characteristic energy of the spin resonance $E_\text{res}=12.5$~meV is smaller than twice the size of the superconducting gap ($2Δ$). The broad energy feature of the dynamical susceptibility of the spin resonance can be explained by the RPA calculations, in which the different superconducting gaps on different Fermi surfaces are taken into account. Our INS and PRA studies demonstrate that the superconducting pairing nature in CaKFe$_4$As$_4$ is the $s_\pm$ symmetry.

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