Searching for heavy fermion (HF) states in non-f-electron systems becomes an interesting issue, especially in the presence of magnetism, and can help explain the physics of complex compounds. Using angle-resolved photoemission spectroscopy, scanning tunneling microscopy, physical properties measurements, and the first-principles calculations, we observe the HF state in a 3d-electron van der Waals ferromagnet, Fe₃GeTe₂. Upon entering the ferromagnetic state, a massive spectral weight transfer occurs, which results from the exchange splitting. Meanwhile, the Fermi surface volume and effective electron mass are both enhanced. When the temperature drops below a characteristic temperature T*, heavy electrons gradually emerge with further enhanced effective electron mass. The coexistence of ferromagnetism and HF state can be well interpreted by the dual properties (itinerant and localized) of 3d electrons. This work expands the limit of ferromagnetic HF materials from f- to d-electron systems and illustrates the positive correlation between ferromagnetism and HF state in the 3d-electron material, which is quite different from the f-electron systems.

中文翻译：

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范德华流动铁磁体 Fe3GeTe2 中近藤晶格行为的出现。


在非 f 电子系统中寻找重费米子 (HF) 态成为一个有趣的问题，特别是在存在磁性的情况下，并且可以帮助解释复杂化合物的物理学。使用角分辨光电子能谱、扫描隧道显微镜、物理性质测量和第一原理计算，我们观察了 3d 电子范德华铁磁体 Fe ₃ GeTe ₂中的 HF 态。进入铁磁态后，会发生大量光谱权重转移，这是由交换分裂引起的。同时，费米表面积和有效电子质量均有所增加。当温度降至特征温度T *以下时，重电子逐渐出现，有效电子质量进一步增强。铁磁性和 HF 态的共存可以通过 3d 电子的双重特性（巡回和定域）来很好地解释。这项工作将铁磁HF材料的极限从f电子系统扩展到d电子系统，并说明了3d电子材料中铁磁性与HF态之间的正相关性，这与f电子系统有很大不同。