元素插层对过渡金属二硫族化合物1T-TaS2中电荷密度波的调控研究

Charge-density wave (CDW) is an important concept in the field of condensed matter physics. The physical nature of CDW is still an open question so far. The rich set of CDW states in the layered transition metal dichalcogenide 1T-TaS2 makes it a very good platform to study the nature of CDW. Recently, a vertical stacking of CDW with some unknown order is found to exist in the system, which significantly influences the physical properties of 1T-TaS2. The stacking order of CDW and the role of interlayer coupling still need to be figured out. Element intercalation can change the interlayer distance, carrier density, orbital orders etc. to control the interlayer coupling and stacking mode of CDW in the system. In this project, we plan to investigate CDW in intercalated compound 1T-TaS2. We will intercalate elements with different atomic radius, valence, magnetism, such as alkali metal, alkali earth metal, 3d transition metal, etc, to 1T-TaS2 single crystal. We will investigate the intercalation induced influences on CDW superlattice by performing detailed structural characterizations, and the variations of CDW-related physical properties by electrical transport, heat transport, and magnetism measurements. Density functional theory calculations will be performed to explain the experimental observations and the role of interlayer coupling on CDW. The study of this project can help to figure out the nature of CDW and explore possible applications of the novel material 1T-TaS2.

电荷密度波(Charge-density wave, CDW)是凝聚态物理中一个重要的概念，其物理本质至今仍有待澄清。过渡金属二硫族化合物1T-TaS2表现出丰富的CDW态，是研究CDW的理想体系。研究指出1T-TaS2中CDW在层间方向是按一定模式堆垛而成，这种堆垛显著影响其宏观性质，但堆垛的具体模式尚不清楚，层间耦合与CDW的关系有待研究。对该体系进行元素插层能调控层间距离、载流子浓度、轨道有序等性质，从而调控层间耦合，改变CDW的堆垛方式。本项目将制备不同原子半径、价态、磁性的元素(如碱金属、碱土金属、3d过渡金属等)插层的1T-MxTaS2单晶样品，通过结构表征手段观察插层对CDW超结构的影响，通过电、磁、热等测量手段表征材料的CDW及其相关物性，结合理论计算，对CDW与层间耦合的关系进行研究。本项目研究可以为澄清CDW的本质提供参考，也可以为开发1T-TaS2的应用潜力提供帮助。

以1T-TaS2为代表的过渡金属二硫族化合物表现出丰富、多样的量子序，如电荷密度波（CDW）态、超导电性等，是研究多重量子序调控的理想体系。本项目以1T-TaS2为研究对象，通过元素插层、压力、应力等手段系统开展了层间耦合对1T-TaS2中CDW和超导电性等量子序的调控规律研究。得到了1T-TaS2在物理压力和化学压力下的完整电子相图，揭示了压力对1T-TaS2基态性质调控的物理机理。通过构筑不同衬底的薄层材料，结合扫描隧道显微镜/谱、拉曼测量和第一性原理计算，从理论和实验角度全面系统地研究了层间耦合作用对1T-TaS2中量子序调控的物理规律。同时，开展了不同外场环境下，如光场、电场、应力场及单层水分子吸附对1T-TaS2中量子序调控的研究，拓展了1T-TaS2在未来器件中的应用属性。本项目研究不仅为理解CDW的本质提供参考，还为开发1T-TaS2的应用潜力提供帮助。受项目资助发表论文28篇，包括1篇PNAS，1篇PRL，4篇Nano Lett.和13篇PRB/M等学术论文。