$$ {The importance of the spin-orbit coupling (SOC) effect in Fe-based superconductors (FeSCs) has recently been under hot debate. Considering the Hund’s coupling-induced electronic correlation, the understanding of the role of SOC in FeSCs is not trivial and still elusive. Here, through a comprehensive study of ${}^{77}$Se and ${}^{57}$Fe nuclear magnetic resonance, a nontrivial SOC effect is revealed in the nematic state of FeSe. Firstly, the orbital-dependent spin susceptibility, determined by the anisotropy of the ${}^{57}$Fe Knight shift, indicates a predominant role from the 3 orbital, which suggests the coexistence of local and itinerant spin degrees of freedom (d.o.f.) in the FeSe. Then, we reconfirm that the orbital reconstruction below the nematic transition temperature ( $\sim$ 90 K) happens not only on the 3 and 3 orbitals but also on the 3 orbital, which is beyond a trivial ferro-orbital order picture. Moreover, our results also indicate the development of a coherent coupling between the local and itinerant spin d.o.f. below , which is ascribed to a Hund’s coupling-induced electronic crossover on the orbital. . The present work not only reveals a nontrivial SOC effect in the nematic state but also sheds light on the mechanism of nematic transition in FeSe.

中文翻译：

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FeSe中自旋轨道交织的向列态

$${最近，自旋轨道耦合（SOC）效应在铁基超导体（FeSC）中的重要性受到了激烈的争论。考虑到Hund的耦合引起的电子相关性，对SOC在FeSC中的作用的理解并不容易，而且仍然难以捉摸。在这里，通过对${}^{77}$硒和 ${}^{57}$Fe核磁共振表明，在FeSe的向列状态下，具有很重要的SOC效应。首先，取决于轨道各向异性的自旋磁化率${}^{57}$Fe Knight位移表示从3轨道起的主要作用，这表明FeSe中局部和巡回自旋自由度（dof）并存。然后，我们确认在向列相变温度以下（$〜$90 K）不仅发生在3和3轨道上，而且发生在3轨道上，这超出了平凡的铁轨道有序图。此外，我们的研究结果还表明，下面的局部自旋自由度和自旋自由度之间存在相干耦合，这归因于亨德耦合在轨道上引起的电子交叉。。目前的工作不仅揭示了向列状态下SOC的微不足道的作用，而且揭示了FeSe向列相转变的机理。