关联材料超薄膜的原位电荷调控和电子结构研究

The manipulation of correlated material systems and the discovery of novel phases promote the development of condensed matter physics. In recent years, the combination of thin-film growth and in-situ angle-resolved photoelectron spectroscopy (OMBE-ARPES) allows atomic-scale multi-degree-of-freedom control and electronic structure study, and a group of artificial ultra-thin film systems with strong correlation was developed. Novel phases are likely emerging in the Mott phase / ordered phase boundary regions of these systems. However, due to the lack of available in-situ charge control technology, these critical regions of phase diagrams cannot be explored. Therefore, we propose to develop OMBE-ARPES-compatible in-situ charge control technology. By combining surface K doping and field effect means, charge doping control will be conducted in LaNiO3 and other strongly correlated ultra-thin film systems to reach the critical regions of the phase diagram. We will study the evolution of electronic structure by in-situ angle resolved photoelectron spectroscopy, reveal the correlated electron behavior and possible novel phases near the boundary of the Mott insulation /ordered phase transition, which will deepen our physical understanding of the correlated electronic systems, and will also facilitate the discovery and application of novel physical properties.

对关联材料体系的参数调控和新奇物相的发现推动着凝聚态物理的发展。近年来薄膜生长和角分辨光电子能谱测量原位结合技术（OMBE-ARPES）的发展，提供了对关联体系进行原子尺度多自由度调控和电子结构测量的手段，在一大批人工超薄膜体系中发现强关联Mott相/有序相。在这些体系的Mott相/有序相边界区域很可能存在新奇物相，然而由于缺乏可用的原位电荷调控技术，无法对这些相图关键区域进行探索。因此申请人提出发展与OMBE-ARPES兼容的原位电荷调控技术。结合表面K掺杂和场效应手段，对LaNiO3等强关联超薄膜体系进行电荷调控以达到相图关键区域，并利用原位角分辨光电子能谱观测电子结构演化，从而揭示在Mott绝缘/有序相转变附近相图空间的关联电子行为和可能的新奇物相，这将加深我们对关联电子体系的物理理解，也将促进新奇关联物性的发现和实际应用。

本项目成功实现原位电压调控的角分辨光电子能谱测量技术，并应用于关联电子体系的研究，主要进行了对Ba0.5K0.5Fe2As2铁基超导体系、SrVO3超薄膜的原位电荷调控和电子结构研究。此外，我们还结合同步辐射角分辨光电子能谱与共振散射，对BaAg2As2中的类密度波相变、CrAs中螺旋磁有序随DM相互作用强度演化作出深入揭示，对铁基超导中的带宽调控统一图像进行了综述。本项目的研究结果加深了我们对于多种关联电子体系量子序演化机理的认识，所研发的原位调控技术也将用于更广泛的物性调控与机理研究。