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).
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