Ning Zhongfeng, Qian Jiahui, Liu Yixin, Chen Fan, Zhang Mingzhu, Deng Liwei, Yuan Xinli, Ge Qingqin, Jin Hua, Zhang Guanqun, Peng Wei, Qiao Shan, Mu Gang, Chen Yan, Li Wei
State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
National Key Laboratory of Materials for Integrated Circuits, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.
Nano Lett. 2024 Jun 12;24(23):7134-7141. doi: 10.1021/acs.nanolett.4c02500. Epub 2024 Jun 3.
The coexistence of superconductivity and ferromagnetism is a long-standing issue in superconductivity due to the antagonistic nature of these two ordered states. Experimentally identifying and characterizing novel heterointerface superconductors that coexist with magnetism presents significant challenges. Here, we report the observation of two-dimensional long-range ferromagnetic order in a KTaO heterointerface superconductor, showing the coexistence of superconductivity and ferromagnetism. Remarkably, our direct current superconducting quantum interference device measurements reveal an in-plane magnetization hysteresis loop persisting above room temperature. Moreover, first-principles calculations and X-ray magnetic circular dichroism measurements provide decisive insights into the origin of the observed robust ferromagnetism, attributing it to oxygen vacancies that localize electrons in nearby Ta 5 states. Our findings suggest KTaO heterointerfaces as time-reversal symmetry breaking superconductors, injecting fresh momentum into the exploration of the intricate interplay between superconductivity and magnetism enhanced by the strong spin-orbit coupling inherent to the heavy Ta in 5 orbitals.
由于这两种有序状态的对抗性质，超导性和铁磁性的共存是超导领域长期存在的问题。通过实验识别和表征与磁性共存的新型异质界面超导体面临重大挑战。在此，我们报告了在一种KTaO异质界面超导体中观察到二维长程铁磁序，表明超导性和铁磁性共存。值得注意的是，我们的直流超导量子干涉器件测量揭示了在室温以上持续存在的面内磁化滞后回线。此外，第一性原理计算和X射线磁圆二色性测量为观察到的强铁磁性的起源提供了决定性见解，将其归因于使附近Ta 5态中的电子局域化的氧空位。我们的发现表明KTaO异质界面是时间反演对称性破缺的超导体，为重Ta 5轨道固有的强自旋轨道耦合增强的超导性和磁性之间复杂相互作用的探索注入了新的动力。
