Research progress and prospect of ambient-pressure nickelate superconducting thin films

Nickelate superconductors constitute the third unconventional high-temperature superconducting family after copper-based superconductors and iron-based superconductors, and have been a research hotspot in the fields of superconducting materials and physics in recent years. Among them, ambient-pressure nickelate superconducting thin films have attracted significant attention due to their convenience in physical research and potential future applications. This review summarizes recent advances in the study of nickelate superconducting thin films under ambient pressure, with a focus on film synthesis, property modulation, and mechanistic investigation of infinite-layer and bilayer Ruddlesden-Popper (RP) phase nickelates. We systematically analyze the characteristics and applicability of key fabrication techniques, including pulsed laser deposition (PLD), oxide molecular beam epitaxy (OMBE), and gigantic-oxidative atomic-layer-by-layer epitaxy (GOALL-Epitaxy). The research results demonstrate that through multi-element doping and strain engineering, the superconducting transition temperature of infinite-layer nickelate film has been enhanced to nearly 40 K. Moreover, bilayer RP nickelate thin films have achieved superconducting transitions with onset temperatures exceeding 60 K at ambient pressure, exhibiting zero resistance, complete diamagnetism, and unconventional superconducting phase diagrams. We provide a outlook regarding the further development of nickelate thin film fabrication technologies, the discovery of novel material systems, and the elucidation of their microscopic pairing mechanisms.