二维层状关联电子材料的奇异电子态与调控研究

In two-dimensional (2D) layered strongly-correlated electron materials, many exotic electronic states were closely related to the phase competition arising from the strong interactions among charge, spin, orbit and lattice, including superconductor, charge density wave, huge magnetoresistance effect and so no. However, the microscopic mechanism of these nontrivial phenomena is still not clear. In this proposal, we intend to take 2D correlated electron materials as the main research object, using new surface and interface chemical methods including guest molecules intercalation and surface modification, control the charge, spin, orbit and lattice ordered parameters to change the balance of internal phase competition in 2D layered correlated materials so that to explore new physical behaviors and quantum states. Using advanced characterization techniques with high spatial resolution, energy and momentum resolution to analyze the changes of local microstructure and electronic structure near the Fermi surface in the 2D layered correlated materials, revealing the law of phase transitions and the relationship between local effects and collective behaviors. In combination with theoretical simulation, explore the inherent physic of phase transformation and exotic electronic states of 2D correlated electron materials to provide guidance for designing new functional correlated electron materials. This study will not only contribute to the understanding of the complex interactions within 2D correlated electron systems, but also be important to the exploration for novel physical phenomena and the development of basic materials research.

在二维层状关联电子材料中，许多奇异电子态是由电荷、自旋、轨道和晶格间强相互作用导致的相竞争引起的，包括超导、电荷密度波和巨磁阻效应等，但这些新奇电子态形成的微观机制仍然不清楚。本项目拟以二维层状关联电子材料为主要研究对象，采用客体分子插层和表面修饰等表-界面化学新方法实现对电荷、自旋、轨道和晶格序参量的调控，改变二维层状关联材料内部各种竞争相的平衡，探索新的物理内容和新型量子态。通过高空间分辨率、能量与动量分辨率等先进表征技术对二维关联电子材料相变导致的局域微结构和费米面附近电子结构变化进行解析，揭示相变规律，以及局域效应与集体行为的关联。并结合理论模拟，探究二维关联电子材料相变和奇异电子态的物理本质，为设计新型功能关联电子材料提供指导。这项研究将不仅有助于二维关联电子体系内复杂相互作用的理解，而且对物理新现象的探索和基础材料研究的发展具有重要意义。

二维层状关联电子材料因其内部电荷、自旋、轨道和晶格间强相互作用诱导了许多有趣的相变现象，如，超导、电荷密度波和巨磁阻等，具有重要的理论研究和实际应用意义。然而，这些新奇电子态的调控手段仍然有限，并且相变的微观机制仍然不清楚。针对这些问题，在本项目执行过程中，我们利用二维层状关联电子材料独特的层状结构和极大的比表面积，发展了大单晶溶剂热插锂剥离法、二茂钴分子插层法和范德华层间外延生长法等表界面化学调控法，成功获得了高产率的具有几十微米的金属态单层TaS2纳米片，由非超导非铁磁成分构建的超导-铁磁共存体系和超顺磁纳米晶修饰诱导的p-n型载流子转变和超低热导等新型磁电性质。通过高分辨透射电子显微镜、扫描隧道显微镜、角分辨光电子能谱和电子顺磁共振谱等对二维关联电子材料的界面局域微观结构、费米能级附近电子结构和电子自旋态等进行观察，揭示了界面电荷转移、层间自旋态转变和磁畴转动等表界面调控的相互作用方式，阐明了这些新奇电子态产生的机理，为理解强关联电子体系相变行为的微观机制提供了实验支持。本项目研究将为大尺寸二维关联电子材料制备和新型磁电性质调控提供了借鉴。