Evidence of electron interaction with an unidentified bosonic mode in superconductor CsCa2Fe4As4F2

作者：Peng Li, Sen Liao, Zhicheng Wang, Huaxun Li, Shiwu Su, Jiakang Zhang, Ziyuan Chen, Zhicheng Jiang, Zhengtai Liu, Lexian Yang, Linwei Huai, Jun-Feng He, Shengtao Cui, Zhe Sun, Y. J. Yan, Guang‐Han Cao, Dawei Shen, Juan Jiang, Donglai Feng · 发表于：Nature Communications · 年份：2024 · DOI：10.1038/s41467-024-50833-9 · 被引用次数：7 · 研究领域：Iron-based superconductors research、Rare-earth and actinide compounds、Inorganic Fluorides and Related Compounds

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 CsCa2Fe4As4F2 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 $$\Gamma -{{\rm{{M}}}}$$ direction at the band with dxz orbital character and vanishes when approaching the $$\Gamma -{{\rm{{X}}}}$$ 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 (~ $$9\pm 1$$ 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. The kink structure in the band dispersion can be linked to electron-boson interaction and has been reported in unconventional superconductors. Here the authors observe an orbital selective and momentum dependent kink feature in an Fe-based superconductor, which is highly correlated with superconductivity.