Sukhenko I V, Karbivskyy V L
Kurdyumov Institute for Metal Physics of the NAS of Ukraine, 36 Acad. Vernadsky Boulevard, Kyiv 03142, Ukraine.
J Phys Condens Matter. 2024 Dec 12;37(8). doi: 10.1088/1361-648X/ad9804.
A Copper-substituted lead apatite, named LK-99 by its authors, has recently emerged as a candidate for the world's first ambient-conditions superconductor, but has since not demonstrated the anticipated properties when subject to independent scrutiny. In this review we cover the experimental and theoretical studies that have been dedicated to this unusual material, while briefly discussing the original arXiv papers. So far, all the synthesis methods result in the formation of a multiphase material with unpredictable structure and unstable stoichiometry. This is a core reason why the studies discussed in the review yield different results when it comes to magnetic, electrophysical properties and even visual appearance of the material. DFT studies of the electronic structure of PbCu(PO)O are reviewed and compared with our original calculations, and the limitations of the DFT approach are discussed. While reviewing theoretical publications on the matter, we bring forward the flat-band superconductivity model and discuss the nature of flat bands and their ability to sustain superconducting transport in the model material. The possibility of the compound being a Mott insulator, given the specifics of its electronic structure, as well as the role of doping, is highlighted. Finally, we raise the question of viability of achieving superconductivity in doped apatites beyond the LK-99 formula.
一种铜取代的铅磷灰石，其作者将其命名为LK-99，最近成为世界上第一种常温超导体的候选材料，但在接受独立审查时，并未表现出预期的特性。在这篇综述中，我们涵盖了针对这种特殊材料的实验和理论研究，同时简要讨论了最初发表在arXiv上的论文。到目前为止，所有的合成方法都导致形成一种具有不可预测结构和不稳定化学计量比的多相材料。这是为什么在综述中讨论的关于该材料的磁性、电物理性质甚至外观的研究得出不同结果的一个核心原因。我们回顾了对PbCu(PO)O电子结构的密度泛函理论（DFT）研究，并与我们最初的计算进行了比较，还讨论了DFT方法的局限性。在回顾关于这个问题的理论出版物时，我们提出了平带超导模型，并讨论了平带的性质以及它们在模型材料中维持超导传输的能力。鉴于其电子结构的特殊性，强调了该化合物成为莫特绝缘体的可能性以及掺杂的作用。最后，我们提出了在LK-99配方之外的掺杂磷灰石中实现超导性的可行性问题。
