Strong Correlation Between Superconductivity and Ferromagnetism in an Fe-Chalcogenide Superconductor

Abstract

The interplay among topology, superconductivity, and magnetism promises to bring a plethora of exotic and unintuitive behaviors in emergent quantum materials. The family of Fe-chalcogenide superconductors FeTe_<i>x</i>Se_1-<i>x</i> are directly relevant in this context due to their intrinsic topological band structure, high-temperature superconductivity, and unconventional pairing symmetry. Despite enormous promise and expectation, the local magnetic properties of FeTe_<i>x</i>Se_1-<i>x</i> remain largely unexplored, which prevents a comprehensive understanding of their underlying material properties. Exploiting nitrogen vacancy (NV) centers in diamond, here we report nanoscale quantum sensing and imaging of magnetic flux generated by exfoliated FeTe_<i>x</i>Se_1-<i>x</i> flakes, demonstrating strong correlation between superconductivity and ferromagnetism in FeTe_<i>x</i>Se_1-<i>x</i>. The coexistence of superconductivity and ferromagnetism in an established topological superconductor opens up new opportunities for exploring exotic spin and charge transport phenomena in quantum materials. The demonstrated coupling between NV centers and FeTe_<i>x</i>Se_1-<i>x</i> may also find applications in developing hybrid architectures for next-generation, solid-state-based quantum information technologies.