XAS/XES study of novel Ni+ oxyfluorides

The novel Ni+ superconductors were found only in late 2020, but have already sparked the field of superconductor research with new enthusiasm. This is due to their similarities (and crucial differences) when compared to the high-Tc cuprate superconductors. The currently known Ni superconductors are all very thin films and the question remains whether the superconductivity in these films is related to interfacial effects. There is thus a great need for bulk Ni+ superconductors. In this work we characterize some promising Ni+ containing oxyfluoride materials that could serve as host structures for future bulk Ni+ superconductors. We wish to understand the local coordination and Ni+ electronic structure to better be able to tune the materials' properties in the future.新型一价镍基超导体（Ni+ superconductors）虽直至2020年末才被发现，却迅速掀起了超导体研究领域的新一轮热潮。这是因为相较于高临界温度铜基超导体（high-Tc cuprate superconductors），二者既有相似之处，亦存在关键差异。目前已发现的一价镍基超导体均为超薄膜，而这类薄膜中的超导电性是否与界面效应相关，仍是未解之谜。因此，开发块体一价镍基超导体的需求极为迫切。本工作对若干极具应用前景的含一价镍氧氟化物（oxyfluoride）材料开展了表征研究，这类材料可作为未来块体一价镍基超导体的宿主结构（host structures）。我们期望阐明其局域配位（local coordination）与一价镍的电子结构（electronic structure），以便未来能够更精准地调控该类材料的物理性能。