The discovery of high-temperature (high-TC) superconductivity in nickelates represents an important breakthrough in condensed matter physics. In particular, the realization of high-TC superconductivity in Ruddlesden-Popper bilayer nickelate films under ambient pressure provides a unique opportunity to examine the electronic structure by angle-resolved photoemission spectroscopy (ARPES). In this video review article, we summarize and highlight our recent progress in Ruddlesden-Popper bilayer nickelate films. Technically, an ultrahigh-vacuum cryogenic sample quenching and transfer technique is developed to overcome the oxygen loss issue of the superconducting films, and laser-based ARPES measurements are performed to get high-quality data. Scientifically, a nodeless superconducting gap, a pseudogap and an electron-boson coupling are observed. The nodeless superconducting gap favors s-wave (s±) pairing symmetry, and the electron-boson coupling provides new insight into the possible pairing glue for high-TC superconductivity. This article reviews the above key observations in a video format, aiming to stimulate future investigations in the field of nickelate superconductors.
These works were supported by the Scientific Research Innovation Capability Support Project for Young Faculty (SRICSPYF-ZY2025069), the National Key Research and Development Program of China (2024YFA1408100), and the CAS Superconducting Research Project (grant no. SCZX-0101).
1. D. Li, K. Lee, B.Y. Wang, M. Osada, S. Crossley, H.R. Lee, Y. Cui, Y. Hikita, and H.Y. Hwang, Superconductivity in an infinite-layer nickelate, Nature 572, 624 (2019).
2. G.A. Pan, D.F. Segedin, H. LaBollita, Q. Song, E.M. Nica, B.H. Goodge, A.T. Pierce, S. Doyle, S. Novakov, D.C. Carrizales, A.T. N’Diaye, P. Shafer, H. Paik, J.T. Heron, J.A. Mason, A. Yacoby, L.F. Kourkoutis, O. Erten, C.M. Brooks, A.S. Botana, and J.A. Mundy, Superconductivity in a quintuple-layer square-planar nickelate, Nat. Mater. 21, 160 (2022).
3. H. Sun, M. Huo, X. Hu, J. Li, Z. Liu, Y. Han, L. Tang, Z. Mao, P. Yang, B. Wang, J. Cheng, D.-X. Yao, G.-M. Zhang, and M. Wang, Signatures of superconductivity near 80 K in a nickelate under high pressure, Nature 621, 493 (2023).
4. Y. Zhang, D. Su, Y. Huang, Z. Shan, H. Sun, M. Huo, K. Ye, J. Zhang, Z. Yang, Y. Xu, Y. Su, R. Li, M. Smidman, M. Wang, L. Jiao, and H. Yuan, High-temperature superconductivity with zero resistance and strange-metal behaviour in La₃Ni₃O₇−δ, Nat. Phys. 20, 1269 (2024).
5. N. Wang, G. Wang, X. Shen, J. Hou, J. Luo, X. Ma, H. Yang, L. Shi, J. Dou, J. Feng, J. Yang, Y. Shi, Z. Ren, H. Ma, P. Yang, Z. Liu, Y. Liu, H. Zhang, X. Dong, Y. Wang, K. Jiang, J. Hu, S. Nagasaki, K. Kitagawa, S. Calder, J. Yan, J. Sun, B. Wang, R. Zhou, Y. Uwatoko, and J. Cheng, Bulk high-temperature superconductivity in pressurized tetragonal La₂PrNi₂O₇, Nature 634, 579 (2024).
6. Y. Zhu, D. Peng, E. Zhang, B. Pan, X. Chen, L. Chen, H. Ren, F. Liu, Y. Hao, N. Li, Z. Xing, F. Lan, J. Han, J. Wang, D. Jia, H. Wo, Y. Gu, Y. Gu, L. Ji, W. Wang, H. Gou, Y. Shen, T. Ying, X. Chen, W. Yang, H. Cao, C. Zheng, Q. Zeng, J.-G. Guo, and J. Zhao, Superconductivity in pressurized trilayer La4Ni4O10−δ single crystals, Nature 631, 531 (2024).
7. Q. Li, Y.-J. Zhang, Z.-N. Xiang, Y. Zhang, X. Zhu, and H.-H. Wen, Signature of superconductivity in pressurized La₄Ni₃O₁₀, Chin. Phys. Lett. 41, 017401 (2024).
8. M. Zhang, C. Pei, D. Peng, X. Du, W. Hu, Y. Cao, Q. Wang, J. Wu, Y. Li, H. Liu, C. Wen, J. Song, Y. Zhao, C. Li, W. Cao, S. Zhu, Q. Zhang, N. Yu, P. Cheng, L. Zhang, Z. Li, J. Zhao, Y. Chen, C. Jin, H. Guo, C. Wu, F. Yang, Q. Zeng, S. Yan, L. Yang, and Y. Qi, Superconductivity in trilayer nickelate La₄Ni₃O₁₀ under pressure, Phys. Rev. X 15, 021005 (2025).
9. M. Shi, D. Peng, K. Fan, Z. Xing, S. Yang, Y. Wang, H. Li, R. Wu, M. Du, B. Ge, Z. Zeng, Q. Zeng, J. Ying, T. Wu, and X. Chen, Pressure induced superconductivity in hybrid Ruddlesden–Popper La₅Ni₃O₁₁ single crystals, Nat. Phys. 21, 1780 (2025).
10. E.K. Ko, Y. Yu, Y. Liu, L. Bhatt, J. Li, V. Thampy, C.-T. Kuo, B.Y. Wang, Y. Lee, K. Lee, J.-S. Lee, B.H. Goodge, D.A. Muller, and H.Y. Hwang, Signatures of ambient pressure superconductivity in thin film La₃Ni₂O₇, Nature 638, 935 (2025).
11. G. Zhou, W. Lv, H. Wang, Z. Nie, Y. Chen, Y. Li, H. Huang, W.-Q. Chen, Y.-J. Sun, Q.-K. Xue, and Z. Chen, Ambient-pressure superconductivity onset above 40 K in (La,Pr)₃Ni₂O₇ films, Nature 640, 641 (2025).
12. Y. Miao, R. Luan, Y. Chen, Z. Ou, G. Zhou, J. Shen, H. Wang, H. Huang, X. Wu, H. Sun, Z. Feng, X. Yong, Y. Li, P. Li, L. Xu, W. Lv, Z. Nie, C. Yue, Y.-J. Sun, W. Chen, H. Yuan, J.-F. Jia, Q.-K. Xue, Z. Chen, and J. He, Electronic structures across superconductor-insulator transition in Ruddlesden-Popper bilayer nickelate films, arXiv:2502.18068v2 (2026).
13. J. Shen, G. Zhou, Y. Miao, P. Li, Z. Ou, Y. Chen, Z. Wang, R. Luan, H. Sun, Z. Feng, X. Yong, Y. Li, L. Xu, W. Lv, Z. Nie, H. Wang, H. Huang, Y.-J. Sun, Q.-K. Xue, J. He, and Z. Chen, Nodeless superconducting gap and electron-boson coupling in (La,Pr,Sm)₃Ni₂O₇ films, Science 392, 1396 (2026).
14. P. Li, G. Zhou, W. Lv, Y. Li, C. Yue, H. Huang, L. Xu, J. Shen, Y. Miao, W. Song, Z. Nie, Y. Chen, H. Wang, W. Chen, Y. Huang, Z.-H. Chen, T. Qian, J. Lin, J. He, Y.-J. Sun, Z. Chen, and Q.-K. Xue, Angle-resolved photoemission spectroscopy of superconducting (La,Pr)₃Ni₂O₇/SrLaAlO₄ heterostructures, Natl. Sci. Rev. 12, nwaf205 (2025).
15. T. Valla, A.V. Fedorov, P.D. Johnson, and S.L. Hulbert, Many-body effects in angle-resolved photoemission: quasiparticle energy and lifetime of a Mo(110) surface state, Phys. Rev. Lett. 83, 2085 (1999).
16. S. LaShell, E. Jensen, and T. Balasubramanian, Nonquasiparticle structure in the photoemission spectra from the Be (0001) surface and determination of the electron self energy, Phys. Rev. B 61, 2371 (2000).
This video article features an AI-assisted digital presenter. AI technology was used solely for video production, while all scientific content was provided and approved by the authors.
