CeSb2中线性色散电子态的拓扑性质及其与f电子的关系

The strongly correlated character and extremely low energy scale of f-electron systems still challenge researchers up to now. The combination of f-electron and topological states in the same system will make the involved physics much more complicated and also interesting. The origin of the topological state in f-electron system and its interaction with f electrons are undoubtedly research hotspots and difficulties in the field of condensed matter physics. With previous investigation and study, we find that CeSb2 compound is likely to be a strongly correlated topological material. Additionally, it is easy to tune the magnetism and condition of the f electrons of CeSb2, which makes this compound an ideal material to study the relationship among f electrons, topological state and magnetism. We propose to study the electronic structures of CeSb2 with angle-resolved photoemission spectroscopy, physical measurement and first-principles calculations. On one hand, we propose to study the topological properties of the linear band dispersion and the physical origin of the negative magnetic resistance. On the other hand, we propose to study the interaction between the linear band dispersion and f electrons by multiple means of regulation. By this research, we expect to illuminate the topological properties of the linear band dispersion in CeSb2 and have a deep understanding of the relationship among strongly correlated electron, linear-dispersive electronic state and magnetic state.

由于f电子体系具有强关联特性和低能量尺度，这对于实验和理论研究而言都充满了挑战。而当f电子体系与具有拓扑性质的电子态相结合时，无疑使得该体系更加复杂和有趣。拓扑态在该体系中的起源以及其与f电子的关系是目前凝聚态物理领域的研究热点和难点。通过前期调研和探索研究，我们发现CeSb2有望成为强关联拓扑材料家族中的新成员。并且由于其f电子状态和磁结构易于调节，该材料是研究f电子、拓扑电子态以及磁性关系的理想体系。本项目拟采用角分辨光电子能谱技术、物性测量以及第一性原理计算等手段研究f电子材料CeSb2的电子结构。一方面研究CeSb2中线性色散能带的拓扑性质以及负磁阻现象的物理起源，另一方面通过多种调节手段研究强关联体系中的线性色散能带与f电子的相互作用。拟通过该课题，阐明该材料中线性色散电子态的拓扑性质，深入系统地理解强关联电子、线性色散电子态以及磁性的相互作用及其演化规律。

通过本项目的实施，我们成功利用助熔剂方法制备出高质量厘米量级的CeSb2和Ce1-xLaxSb2单晶样品。利用综合物性测量系统，获得了其基本的电输运性质和磁性质，发现CeSb2具有典型的重费米子特征，并且在低温下具有四个磁有序转变，不仅如此，当电流和磁场平行时，其磁阻率呈现出负磁阻行为。随后，我们主要利用角分辨光电子能谱结合第一性原理计算，发现CeSb2中存在明显的线性色散能带，表明该材料是属于拓扑材料，并且f电子呈现出随着温度演化的局域巡游转变特征。然而结合CeSb2和Ce1-xLaxSb2单晶的对比实验，我们发现其拓扑特性并不起源于f电子，而且拓扑态与f电子能带无明显耦合。相关结果对于认识新型强关联拓扑材料具有重要意义。

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