Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Phys Rev Lett. 2018 Jun 29;120(26):267003. doi: 10.1103/PhysRevLett.120.267003.
We report an inelastic neutron scattering study on the spin resonance in the bilayer iron-based superconductor CaKFe_{4}As_{4}. In contrast to its quasi-two-dimensional electron structure, three strongly L-dependent modes of spin resonance are found below T_{c}=35 K. The mode energies are below and linearly scale with the total superconducting gaps summed on the nesting hole and electron pockets, essentially in agreement with the results in cuprate and heavy fermion superconductors. This observation supports the sign-reversed Cooper pairing mechanism under multiple pairing channels and resolves the long-standing puzzles concerning the broadening and dispersive spin resonance peak in iron pnictides. More importantly, the triple resonant modes can be classified into odd and even symmetries with respect to the distance of Fe-Fe planes within the Fe-As bilayer unit. Thus, our results closely resemble those in the bilayer cuprates with nondegenerate spin excitations, suggesting that these two high-T_{c} superconducting families share a common nature.
我们报告了对双层铁基超导体 CaKFe_{4}As_{4}中自旋共振的非弹性中子散射研究。与它的准二维电子结构相反，在 T_{c}=35 K 以下发现了三个强烈依赖于 L 的自旋共振模式。这些模式的能量低于并与嵌套空穴和电子口袋上的总超导能隙线性标度，这与铜酸盐和重费米子超导体的结果基本一致。这一观察结果支持了多配对通道下符号反转的 Cooper 配对机制，并解决了铁磷化物中自旋共振峰展宽和弥散的长期难题。更重要的是，三重共振模式可以根据 Fe-As 双层单元内 Fe-Fe 平面之间的距离分为奇数和偶数对称。因此，我们的结果与非简并自旋激发的双层铜酸盐非常相似，这表明这两个高温超导家族具有共同的性质。
