近期，南方科技大学薛其坤教授和陈卓昱副教授团队发现（La,Pr）₃Ni₂O₇薄膜在40 K以上表现出常压超导性。相关论文发表在2025年2月17日出版的《自然》杂志上。

高压下双层镍酸盐超导体的发现揭开了高转变温度（高T_C）超导性的新篇章。然而，高压条件和杂质相的存在阻碍了对其超导性能和潜在应用的全面研究。

研究组报道了双层镍酸盐外延薄膜在McMillan极限（40K）以上的常压超导性。在SrLaAlO₄基底上使用巨大的氧化原子逐层外延（GOALL epitaxy）生长了三个晶胞（3UC）厚的La_2.85Pr_0.15Ni₂O₇纯相单晶薄膜。电阻率测量和磁场响应表明起始T_C=45 K。向零电阻的转变表现出与Berezinskii–Kosterlitz–Thouless（BKT）样行为一致的特征，T_BKT=9 K。通过互感装置在TM=8 K时观察到迈斯纳反磁效应，与BKT样转变一致。

面内和面外临界磁场表现出各向异性。扫描透射电子显微镜（STEM）图像和X射线互易空间映射（RSM）表明，双层镍酸盐薄膜在NiO₂平面相对于块体的约2%相干外延压缩应变下呈四方相。该发现为在环境压力条件下全面研究镍酸盐超导体以及通过异质结构中的应变工程探索更高转变温度下的超导性铺平了道路。

Title: Ambient-pressure superconductivity onset above 40 K in (La,Pr)3Ni2O7 films

Author: Zhou, Guangdi, Lv, Wei, Wang, Heng, Nie, Zihao, Chen, Yaqi, Li, Yueying, Huang, Haoliang, Chen, Weiqiang, Sun, Yujie, Xue, Qi-Kun, Chen, Zhuoyu

Issue&Volume: 2025-02-17

Abstract: The discovery of bilayer nickelate superconductors under high pressure has opened a new chapter in high-transition temperature (high-TC) superconductivity1-8. However, the high-pressure condition and presence of impurity phases have hindered comprehensive investigations into their superconducting properties and potential applications. Here, we report ambient-pressure superconductivity onset above the McMillan limit (40 K) in bilayer nickelate epitaxial thin films. Three-unit-cell (3UC) thick La2.85Pr0.15Ni2O7 pure-phase single-crystal films are grown using the gigantic-oxidative atomic-layer-by-layer epitaxy (GOALL-Epitaxy) on SrLaAlO4 substrates9. Resistivity measurements and magnetic-field responses indicate onset TC = 45 K. The transition to zero resistance exhibits characteristics consistent with a Berezinskii–Kosterlitz–Thouless (BKT)-like behavior, with TBKT = 9 K. Meissner diamagnetic effect is observed at TM = 8 K via a mutual inductance setup, in agreement with the BKT-like transition. In-plane and out-of-plane critical magnetic fields exhibit anisotropy. Scanning transmission electron microscopy (STEM) images and X-ray reciprocal space mappings (RSMs) reveal that the bilayer nickelate films adopt a tetragonal phase under ~2% coherent epitaxial compressive strain in the NiO2 planes relative to the bulk. Our findings pave the way for comprehensive investigations of nickelate superconductors under ambient pressure conditions and for exploring superconductivity at higher transition temperature through strain engineering in heterostructures.

DOI: 10.1038/s41586-025-08755-z

Source: https://www.nature.com/articles/s41586-025-08755-z