Li Peng, Liao Sen, Wang Zhicheng, Li Huaxun, Su Shiwu, Zhang Jiakang, Chen Ziyuan, Jiang Zhicheng, Liu Zhengtai, Yang Lexian, Huai Linwei, He Junfeng, Cui Shengtao, Sun Zhe, Yan Yajun, Cao Guanghan, Shen Dawei, Jiang Juan, Feng Donglai
Shool of Emerging Technology, University of Science and Technology of China, Hefei, 230026, China.
Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University, Nanjing, 211189, China.
Nat Commun. 2024 Jul 31;15(1):6433. doi: 10.1038/s41467-024-50833-9.
The kink structure in band dispersion usually refers to a certain electron-boson interaction, which is crucial in understanding the pairing in unconventional superconductors. Here we report the evidence of the observation of a kink structure in Fe-based superconductor CsCaFeAsF using angle-resolved photoemission spectroscopy. The kink shows an orbital selective and momentum dependent behavior, which is located at 15 meV below Fermi level along the direction at the band with d orbital character and vanishes when approaching the direction, correlated with a slight decrease of the superconducting gap. Most importantly, this kink structure disappears when the superconducting gap closes, indicating that the corresponding bosonic mode (~ meV) is closely related to superconductivity. However, the origin of this mode remains unidentified, since it cannot be related to phonons or the spin resonance mode (~15 meV) observed by inelastic neutron scattering. The behavior of this mode is rather unique and challenges our present understanding of the superconducting paring mechanism of the bilayer FeAs-based superconductors.
能带色散中的扭结结构通常指的是某种电子 - 玻色子相互作用，这对于理解非常规超导体中的配对至关重要。在此，我们报告了使用角分辨光电子能谱在铁基超导体CsCaFeAsF中观测到扭结结构的证据。该扭结呈现出轨道选择性和动量依赖性行为，它位于具有d轨道特征的能带沿 方向费米能级以下15毫电子伏特处，并且在接近 方向时消失，这与超导能隙的轻微减小相关。最重要的是，当超导能隙关闭时，这种扭结结构消失，表明相应的玻色子模式（~ 毫电子伏特）与超导性密切相关。然而，这种模式的起源仍然不明，因为它与声子或非弹性中子散射观测到的自旋共振模式（~15毫电子伏特）无关。这种模式的行为相当独特，对我们目前对双层铁基超导体超导配对机制的理解提出了挑战。
