Chen Shengru, Zhang Qinghua, Li Xujing, Zhao Jiali, Lin Shan, Jin Qiao, Hong Haitao, Huon Amanda, Charlton Timothy, Li Qian, Yan Wensheng, Wang Jiaou, Ge Chen, Wang Can, Wang Baotian, Fitzsimmons Michael R, Guo Haizhong, Gu Lin, Yin Wen, Jin Kui-Juan, Guo Er Jia
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Adv. 2022 Oct 28;8(43):eabq3981. doi: 10.1126/sciadv.abq3981.
Emergent phenomena at heterointerfaces are directly associated with the bonding geometry of adjacent layers. Effective control of accessible parameters, such as the bond length and bonding angles, offers an elegant method to tailor competing energies of the electronic and magnetic ground states. In this study, we construct unit-thick syntactic layers of cobaltites within a strongly tilted octahedral matrix via atomically precise synthesis. The octahedral tilt patterns of adjacent layers propagate into cobaltites, leading to a continuation of octahedral tilting while maintaining substantial misfit tensile strain. These effects induce severe rumpling within an atomic plane of neighboring layers, further triggering the electronic reconstruction between the splitting orbitals. First-principles calculations reveal that the cobalt ions transit to a higher spin state level upon octahedral tilting, resulting in robust ferromagnetism in ultrathin cobaltites. This work demonstrates a design methodology for fine-tuning the lattice and spin degrees of freedom in correlated quantum heterostructures by exploiting epitaxial geometric engineering.
异质界面处的涌现现象与相邻层的键合几何结构直接相关。有效控制可及参数，如键长和键角，提供了一种巧妙的方法来调整电子和磁基态的竞争能量。在本研究中，我们通过原子精确合成在强倾斜八面体矩阵中构建了单位厚度的钴酸盐句法层。相邻层的八面体倾斜模式传播到钴酸盐中，导致八面体倾斜的延续，同时保持大量的错配拉伸应变。这些效应在相邻层的原子平面内引起严重的褶皱，进一步触发分裂轨道之间的电子重构。第一性原理计算表明，八面体倾斜时钴离子跃迁到更高的自旋态能级，导致超薄钴酸盐中出现强铁磁性。这项工作展示了一种通过利用外延几何工程来微调相关量子异质结构中晶格和自旋自由度的设计方法。
