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 experimental observation of two-dimensional long-range ferromagnetic order in the KTaO3 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, the 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 5d states. Our findings not only suggest KTaO3 heterointerfaces as time-reversal symmetry breaking superconductors, but also inject 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 5d orbitals of KTaO3 heterointerfaces.
@article{arxiv.2302.01549,
title = {Coexistence of ferromagnetism and superconductivity at KTaO$_3$ heterointerfaces},
author = {Zhongfeng Ning and Jiahui Qian and Yixin Liu and Fan Chen and Mingzhu Zhang and Liwei Deng and Xinli Yuan and Qingqin Ge and Hua Jin and Guanqun Zhang and Wei Peng and Shan Qiao and Gang Mu and Yan Chen and Wei Li},
journal= {arXiv preprint arXiv:2302.01549},
year = {2024}
}