CeMIn5(M=Co,Ir)中掺杂对超导态和量子临界效应的影响

Heavy Fermion system is a prototype to study quantum phase transition and unconventional superconductivity. Quantum critical point (QCP) can be accessed through tuning the hybridization between the localized f and itinerant conduction electrons in the system and exotic quantum states with anomalous normal-state behaviors will emerge around the QCP. As a clean and powerful tool for tuning the electronic states of heavy Fermion systems, physical pressure is applied to study the intricate relationships between different ground states such as magnetism and superconductivity and to search for exotic quantum states or emergent phenomena. In this proposal, we will study the heat capacity and resistivity of Cd and Sn doped CeIrIn5 under higher pressure to explore the relationship between c-f hybridization and disorder effect on the unconventional superconductivity. By studying the evolution of Q phase in CeCoIn5 under pressure, we intend to explore the puzzling nature of Q phase under heated debate. To further reveal the effect of Cd doping on the superconductivity in CeIrIn5, we also plan to develop the field angle dependent heat capacity technique and to investigate its superconducting order parameter symmetry under pressure. This project will be of great interest to understand the nature of heavy Fermions and unconventional superconductivity.

重费米子体系是研究量子相变及非常规超导的典型体系，通过调控重费米子体系中局域f电子与传导电子的杂化强度，体系可达到量子临界点。在临界点附近，它表现出许多奇异量子行为，如非费米液体行为、非常规超导等。压力是一种纯净且有效的调控手段：通过研究材料基态随压力的演化，探讨重费米子体系中磁性与超导相互作用机制，可以为理解非常规超导的形成和机理，提供重要的实验证据。本课题拟通过对Cd和Sn掺杂的CeIrIn5开展压力下电阻率和比热的测量，探讨杂化强度和无序度对体系的影响及作用机理；CeCoIn5的Q相是一个存在争议的难题，通过压力下Q相的研究，可深入探讨它的物理机理；发展压力下转角比热这一超导序参量测量方法，研究Cd掺杂CeCoIn5和CeIrIn5在压力下的超导能隙对称性，从而进一步揭示Cd掺杂对超导态的影响。本项目的研究将为重费米子体系磁性与超导相互作用以及非常规超导的机理提供更多的实验证据。

在本项目的资助下，我们主要利用压力、掺杂以及磁场等调控手段研究了几类重费米子材料的磁性、超导相互作用关系以及量子临界行为；利用超导穿透深度等测量手段探索了几种超导材料的超导能隙对称性。在项目执行期间，取得了一些较有意义的结果，共发表致谢SCI论文6篇，其中PNAS一篇，PRB两篇。.项目所取得的主要研究成果如下：（1）合成了新型铁磁重费米子材料CeZnAl3, 为研究量子相变与超导提供了新的材料体系和新的视角；（2）利用压力调控了重费米子Ce-115体系的衍生体系Ce3PdIn11，发现了其超导相随反铁磁序被抑制时出现的反常现象；（3） 利用磁场调控Ce2Sb和Ce2Bi体系，发现其磁致三相共存。（4）进一步澄清了重费米子超导体CeCu2Si2不存在能隙节点，提出了一种新的两能带d-波超导模型，合理解释了先前很多矛盾的实验结果。