深入研究钙钛矿氧化物异质结的界面和电子结构，对于理解二维电子气、界面超导和磁性等非常规界面量子现象和开发相关氧化物薄膜器件至关重要。目前我们对氧化物异质结界面结构的认识局限于传统的晶格失配层面，由于界面晶体对称性差异所引起的晶格畸变，长期以来一直被忽视。本项目拟结合最新的实验进展，利用先进的异质结生长和界面表征技术，研究LaCoO3基异质结界面晶体对称性失配和八面体扭曲状态。我们将采用第一性原理模拟和电子能谱表征，从深层次揭示这种界面结构扭曲对界面电荷转移和自旋态等电子结构和磁学特征的影响，以提出合理的磁矩相互作用模型，为解决长期以来LaCoO3薄膜磁性起源的争论提供新思路。我们还拓展对称性调控（Symmetry Engineering）的概念，将从实验角度提出几种可行的方法来调制界面晶体对称性失配程度，且进一步探索其作为一种新的手段在广义上对材料性能调控的可能性和一般规律。

In-depth knowledge of the lattice structure and electronic structure of perovskite oxide hetero-interfaces is not only crucial to understand the origin of some unconventional quantum phenomena such as two dimensional electron gas, interface conductivity and magnesium but also critical to design oxide thin-film devices for practical applications. Currently our knowledge on the structure of these interfaces is primarily limited in the regime of traditional lattice constant mismatch, however; the lattice distortion induced by interface symmetry mismatch is not appropriately considered for a long time. This proposal will consider the latest experimental progress, combine advanced heterostructural epitaxial growth and interface characterization techniques, to quantify the symmetry mismatch and octahedral distortion in LaCoO3 based interfaces. First-principles simulation and electron energy spectroscopies will be employed to unravel the impact of this structural distortion on the electronic structure, such as interface charge transfer and spin structure, as well as magnetic properties of the interface. Experimental study and theoretical simulation will then be combined to suggest an appropriate magnetic moment interaction model, thus providing new perspective to resolve the long-standing debate regarding the origin of the long-range magnetism for thin film LaCoO3. Finally, we will develop several experimental strategies to realize the “Symmetry Engineering” of heterostructural interface, and propose this new strategy as a general approach to engineer the physical properties of materials.