Xu Hao, Li Hang, Gauquelin Nicolas, Chen Xuejiao, Wu Wen-Feng, Zhao Yuchen, Si Liang, Tian Di, Li Lei, Gan Yulin, Qi Shaojin, Li Minghang, Hu Fengxia, Sun Jirong, Jannis Daen, Yu Pu, Chen Gang, Zhong Zhicheng, Radovic Milan, Verbeeck Johan, Chen Yunzhong, Shen Baogen
Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
Adv Mater. 2024 Jul;36(29):e2313297. doi: 10.1002/adma.202313297. Epub 2024 May 13.
The 2D electron gas (2DEG) at oxide interfaces exhibits extraordinary properties, such as 2D superconductivity and ferromagnetism, coupled to strongly correlated electrons in narrow d-bands. In particular, 2DEGs in KTaO (KTO) with 5d t orbitals exhibit larger atomic spin-orbit coupling and crystal-facet-dependent superconductivity absent for 3d 2DEGs in SrTiO (STO). Herein, by tracing the interfacial chemistry, weak anti-localization magneto-transport behavior, and electronic structures of (001), (110), and (111) KTO 2DEGs, unambiguously cation exchange across KTO interfaces is discovered. Therefore, the origin of the 2DEGs at KTO-based interfaces is dramatically different from the electronic reconstruction observed at STO interfaces. More importantly, as the interface polarization grows with the higher order planes in the KTO case, the Rashba spin splitting becomes maximal for the superconducting (111) interfaces approximately twice that of the (001) interface. The larger Rashba spin splitting couples strongly to the asymmetric chiral texture of the orbital angular moment, and results mainly from the enhanced inter-orbital hopping of the t bands and more localized wave functions. This finding has profound implications for the search for topological superconductors, as well as the realization of efficient spin-charge interconversion for low-power spin-orbitronics based on (110) and (111) KTO interfaces.
氧化物界面处的二维电子气（2DEG）展现出非凡的特性，如二维超导性和铁磁性，且与窄d带中强关联电子相耦合。特别地，具有5d t轨道的KTaO（KTO）中的二维电子气表现出更大的原子自旋 - 轨道耦合以及与晶体面相关的超导性，而SrTiO（STO）中的3d二维电子气则不存在这种特性。在此，通过追踪（001）、（110）和（111）KTO二维电子气的界面化学、弱反局域化磁输运行为及电子结构，明确发现了KTO界面间的阳离子交换。因此，基于KTO的界面处二维电子气的起源与在STO界面观察到的电子重构显著不同。更重要的是，在KTO情形下，随着界面极化随高阶平面增加，对于超导（111）界面，Rashba自旋分裂达到最大值，约为（001）界面的两倍。更大的Rashba自旋分裂与轨道角动量的不对称手性纹理强烈耦合，主要源于t带间增强的轨道间跳跃以及更局域化的波函数。这一发现对于寻找拓扑超导体以及基于（110）和（111）KTO界面实现低功耗自旋轨道电子学的高效自旋 - 电荷相互转换具有深远意义。
