The recent discovery of high temperature superconductivity in nickelate systems has generated tremendous interests in the community. We have successfully synthesized the superconducting thin films of La₂PrNi₂O₇ with T_c^onset = 41.5 K at ambient pressure, and found that the T_c^onset can be enhanced to above 60K under pressure, then it slightly drops down forming a phase diagram with a dome-like shape. Our theoretical calculations yield a cooperative enhancement of magnetic fluctuations between and within the layers and increased metallicity under pressure. These findings highlight the critical role of the interplay between interlayer and intralayer electronic correlations in bilayer nickelate superconductors and point to the potential of tuning T_c through controlled manipulation of the electronic structure and interactions[1]. We also successfully measured the single particle tunneling spectrum after we expose the superconducting layer by using the tip-excavation technique. A dominant gap at about 19 meV is observed and a kink structure appears at about 6-8 meV, the later is interpreted as a second smaller gap. The fittings based on the Dynes model indicate that the dominant gap should have an s-wave structure with low anisotropy, this allows us to select the s⁺⁻-pairing symmetry among the two possibilities: s⁺⁻ and d-wave. The uniform spectra across a relatively long distance suggests a good coherent state in the bilayer nickelates, which is different from the cuprate superconductors and indicates the definite involvement of the less correlated 3d_x2-y2 orbital[2].

References

[1] Qing Li, Jianping Sun, Steffen Bötzel, Mengjun Ou, Zhe-Ning Xiang, Frank Lechermann, Bosen Wang, Yi Wang, Ying-Jie Zhang, Jinguang Cheng, Ilya M. Eremin & Hai-Hu Wen. Nature Communications 17, 3276 (2026).

[2] Shengtai Fan, Mengjun Ou, Marius Scholten, Qing Li, Zhiyuan Shang, Yi Wang, Jiasen Xu, Huan Yang, Ilya M. Eremin, Hai-Hu Wen. arXiv: 2506.01788.