界面超导体LaAlO3/KTaO3中取向依赖的电子-声子耦合
Orientation-dependent electron-phonon coupling in interfacial superconductors LaAlO3/KTaO3
AI总结：
本文利用软X射线角分辨光电子能谱揭示LaAlO3/KTaO3界面超导电性源于准三维电子气，并发现其与Fuchs-Kliewer表面声子的耦合强度随KTaO3晶体学取向变化，更强耦合对应更高超导转变温度，首次证明界面取向可在纳米尺度调控电子-声子耦合。
摘要：
LaAlO3/KTaO3界面涌现的超导电性表现出对KTaO3晶体学取向的神秘依赖。在此，我们通过软X射线角分辨光电子能谱表明，界面超导电性由具有意外准三维特征的移动电子贡献，超越了描述氧化物界面的“二维电子气”图景。在不同取向的界面处，准三维电子气普遍存在，并在空间上与小q的Fuchs-Kliewer表面声子重叠。有趣的是，电子与Fuchs-Kliewer声子的耦合强度因界面取向而异，且更强的耦合与更高的超导转变温度相关。我们的结果为取向依赖的超导电性提供了自然的解释，并首次证明界面取向可以在数纳米范围内影响电子-声子耦合强度，这可能对氧化物界面的应用具有深远意义。
英文摘要：
The emergent superconductivity at the LaAlO3/KTaO3 interfaces exhibits a mysterious dependence on the KTaO3 crystallographic orientations. Here we show, by soft X-ray angle-resolved photoemission spectroscopy, that the interfacial superconductivity is contributed by mobile electrons with unexpected quasi-three-dimensional character, beyond the "two-dimensional electron gas" scenario in describing oxide interfaces. At differently-oriented interfaces, the quasi-three-dimensional electron gas ubiquitously exists and spatially overlaps with the small q Fuchs-Kliewer surface phonons. Intriguingly, electrons and the Fuchs-Kliewer phonons couple with different strengths depending on the interfacial orientations, and the stronger coupling correlates with the higher superconducting transition temperature. Our results provide a natural explanation for the orientation-dependent superconductivity, and the first evidence 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.
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