Chen Xiaoyang, Yu Tianlun, Liu Yuan, Sun Yanqiu, Lei Minyinan, Guo Nan, Fan Yu, Sun Xingtian, Zhang Meng, Alarab Fatima, Strocov Vladimir N, Wang Yilin, Zhou Tao, Liu Xinyi, Lu Fanjin, Liu Weitao, Xie Yanwu, Peng Rui, Xu Haichao, Feng Donglai
Advanced Materials Laboratory, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai, China.
School of Physics, Zhejiang University, Hangzhou, China.
Nat Commun. 2024 Sep 4;15(1):7704. doi: 10.1038/s41467-024-51969-4.
Emergent superconductivity at the LaAlO/KTaO interfaces exhibits a mysterious dependence on the KTaO crystallographic orientations. Here by soft X-ray angle-resolved photoemission spectroscopy, we directly resolve the electronic structure of the LaAlO/KTaO interfacial superconductors and the non-superconducting counterpart. We find that the mobile electrons that contribute to the interfacial superconductivity show strong k dispersion. Comparing the superconducting and non-superconducting interfaces, the quasi-three-dimensional electron gas with over 5.5 nm spatial distribution ubiquitously exists and shows similar orbital occupations. The signature of electron-phonon coupling is observed and intriguingly dependent on the interfacial orientations. Remarkably, the stronger electron-phonon coupling signature correlates with the higher superconducting transition temperature. Our observations help scrutinize the theories on the orientation-dependent superconductivity and offer a plausible and straightforward explanation. The interfacial orientation effect that can modify the electron-phonon coupling strength over several nanometers sheds light on the applications of oxide interfaces in general.
LaAlO₃/KTaO₃界面处的超导现象呈现出对KTaO₃晶体取向的神秘依赖性。在此，我们通过软X射线角分辨光电子能谱直接解析了LaAlO₃/KTaO₃界面超导体及其非超导对应物的电子结构。我们发现，对界面超导性有贡献的可移动电子表现出强烈的k色散。对比超导和非超导界面，具有超过5.5纳米空间分布的准三维电子气普遍存在且呈现出相似的轨道占据情况。我们观察到了电子 - 声子耦合的特征，且有趣的是，该特征依赖于界面取向。值得注意的是，更强的电子 - 声子耦合特征与更高的超导转变温度相关。我们的观察结果有助于审视关于取向依赖性超导性的理论，并提供了一个合理且直接的解释。这种能够在几纳米范围内改变电子 - 声子耦合强度的界面取向效应，为一般氧化物界面的应用提供了启示。
