Zhang Yun, Lu Haiyan, Zhu Xiegang, Tan Shiyong, Feng Wei, Liu Qin, Zhang Wen, Chen Qiuyun, Liu Yi, Luo Xuebing, Xie Donghua, Luo Lizhu, Zhang Zhengjun, Lai Xinchun
Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang 621907, China.
Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
Sci Adv. 2018 Jan 12;4(1):eaao6791. doi: 10.1126/sciadv.aao6791. eCollection 2018 Jan.
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, FeGeTe. 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 *, 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.
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，尤其是在存在磁性的情况下，并且有助于解释复杂化合物的物理性质。利用角分辨光电子能谱、扫描隧道显微镜、物理性质测量以及第一性原理计算，我们在一种3d电子范德华铁磁体FeGeTe中观测到了HF态。进入铁磁态时，会发生大量的光谱权重转移，这是由交换劈裂导致的。同时，费米面体积和有效电子质量都增大了。当温度降至特征温度*以下时，重电子逐渐出现，有效电子质量进一步增大。铁磁性和HF态的共存可以通过3d电子的双重性质（巡游性和局域性）得到很好的解释。这项工作将铁磁HF材料的范围从f电子系统扩展到了d电子系统，并阐明了3d电子材料中铁磁性与HF态之间的正相关关系，这与f电子系统有很大不同。
