The cooper pairs in the heavy-fermion superconductor CeCu₂Si₂ are formed of heavy fermions. Therefore, the heavy fermions are fundamental to the emergence of unconventional superconductivity and associated non-Fermi-liquid behavior in the normal state. The interplay between localization and itinerancy manifested on the electronic structure is key for understanding the heavyfermion behavior. Here, via the first-principle density functional theory (DFT) combined with single-site dynamical mean-field theory (DMFT), we investigate the temperature (T) evolution of the electronic structure of CeCu₂Si₂ in the normal state, focusing on the role of the 4f states in the low energy regime. Two characteristic temperature scales of this evolution, which accompanied the heavy-fermion formation, are established. The coherence onset temperature is around 130 K, whereas the heavy-fermion band formation temperature is between 40 and 80 K; both characteristic temperature scales are higher than the transport coherence temperature. Furthermore, the heavy-fermion formation is confirmed by calculating its effective mass variation with the temperature. Based on the calculated T-dependent evolution of the 4f orbital occupancy and electronic structure, an explanation on the behavior of the temperature evolution of the correlation strength of CeCu₂Si₂ is provided. Our results offer a comprehensive microscopic picture of the heavy-fermion formation in CeCu₂Si₂, which is essential for further understanding the emergent superconducting pairing mechanism.

中文翻译：

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CeCu 2 Si 2中伴随重铁离子形成的电子结构演化

重金属费米超导体CeCu ₂ Si ₂中的铜对由重金属费米形成。因此，在正常状态下，重费米子是非常规超导电性和相关非费米液体行为出现的基础。电子结构上显示的定位和迭代之间的相互作用是理解重铁蛋白行为的关键。在这里，通过第一原理密度泛函理论（DFT）结合单点动态平均场理论（DMFT），我们研究了正常状态下CeCu ₂ Si ₂电子结构的温度（T）演化，关于4 f的作用低能状态下的国家。建立了伴随着重费米子形成的这种演化的两个特征温度标度。相干起始温度约为130 K，而重费米子带的形成温度在40至80 K之间。两个特征温度标度均高于传输相干温度。此外，通过计算其有效质量随温度的变化来确认重费米子的形成。根据计算得出的4 f轨道占有率和电子结构的T依赖演化，对CeCu ₂ Si ₂相关强度的温度演化行为进行了解释。提供。我们的结果提供了CeCu ₂ Si _2中重铁原子形成的全面微观图像，这对于进一步了解新兴的超导配对机制至关重要。