Role of optical phonons for normal and superconducting state properties of KTO
ORAL · Invited
Abstract
Emergent superconductivity at the LaAlO$_3$/KTaO$_3$ interfaces exhibits a mysterious dependence on the KTaO$_3$ crystallographic orientations. Here by soft X-ray angle-resolved photoemission spectroscopy, we directly resolve the electronic structure of the LaAlO$_3$/KTaO$_3$ interfacial superconductors and the non-superconducting counterpart. We find that the mobile electrons that contribute to the interfacial superconductivity show strong $k_perp$ dispersion. Comparing the superconducting and non-superconducting interfaces, the quasi-three-dimensional electron gas with over 5.5~nm spatial distribution ubiquitously exists, while the main difference lies on the signature of electron-phonon coupling, which shows intriguingly different strengths depending on the interfacial orientations. Remarkably, the stronger electron-phonon coupling correlates with the higher superconducting transition temperature. Our observations offer a straightforward explanation for the orientation-dependent superconductivity and suggest that interfacial orientations can affect electron-phonon coupling strength over several nanometers, which may have profound implications for the applications of oxide interfaces in general.
*This work is supported in part by the National Natural Science Foundation of China (Grants Nos. 11922403, 11790312, 11888101, 12074074, 12274085, 11934016), Shanghai Rising-Star Program (Grant No. 20QA1401400) and Shanghai Municipal Science and Technology Major Project by Anhui Initiative in Quantum Information Technologies. (Grant No. 2019SHZDZX01).
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Publication:Chen, X.; Yu, T.; Liu, Y.; Sun, Y.; Lei, M.; Guo, N.; Fan, Y.; Sun, X.; Zhang, M.; Alarab, F.; Strokov, V. N.; Wang, Y.; Zhou, T.; Liu, X.; Lu, F.; Liu, W.; Xie, Y.; Peng, R.; Xu, H.; Feng, D. Orientation-Dependent Electron-Phonon Coupling in Interfacial Superconductors LaAlO3/KTaO3. arXiv January 31, 2023. https://doi.org/10.48550/arXiv.2301.13488.
