超导体CsCa$_2$Fe$_4$As$_4$F$_2$中电子与未识别玻色模式相互作用的证据
Evidence of electron interaction with an unidentified bosonic mode in superconductor CsCa$_2$Fe$_4$As$_4$F$_2$
AI总结：
本文利用ARPES在铁基超导体CsCa$_2$Fe$_4$As$_4$F$_2$中发现一个轨道选择性的能带扭折结构，其对应的9 meV玻色模式与超导能隙密切相关，但起源未知，挑战了现有配对机制理解。
摘要：
能带色散中的扭折结构通常指某种电子-玻色子相互作用，这对于理解非常规超导体中的配对机制至关重要。本文报道了利用角分辨光电子能谱在铁基超导体CsCa$_2$Fe$_4$As$_4$F$_2$中观测到扭折结构的证据。该扭折表现出轨道选择性和动量依赖行为，位于费米能级以下15 meV处，沿Γ-M方向出现在具有dxz轨道特征的能带上，并在接近Γ-X方向时消失，同时伴随着超导能隙的轻微减小。最重要的是，当超导能隙闭合时，该扭折结构消失，表明相应的玻色模式（9 meV）与超导电性密切相关。然而，该模式的起源仍未确定，因为它无法与声子或非弹性中子散射观测到的自旋共振模式（15 meV）相关联。该模式的行为相当独特，对目前关于双层FeAs基超导体超导配对机制的理解提出了挑战。
英文摘要：
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 CsCa$_2$Fe$_4$As$_4$F$_2$ 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-M direction at the band with dxz orbital character and vanishes when approaching the Gamma-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 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.
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