Ambient-pressure superconductivity and electronic structures of engineered hybrid nickelate films
Zihao Nie, Yueying Li, Wei Lv, Lizhi Xu, Zhicheng Jiang, Peng Fu, Guangdi Zhou, Wenhua Song, Yaqi Chen, Heng Wang, Haoliang Huang, Junhao Lin, Dawei Shen, Peng Li, Qi-Kun Xue, Zhuoyu Chen
Published: 2025/9/3
Abstract
Ruddlesden-Popper (RP) nickelates have emerged as a crucial platform for exploring the mechanisms of high-temperature superconductivity. However, the Fermi surface topology required for superconductivity remains elusive. Here, we report the thin film growth and ambient-pressure superconductivity of both hybrid monolayer-bilayer (1212) and pure bilayer (2222) structures, together with the absence of superconductivity in hybrid monolayer-trilayer (1313) structure, under identical compressive epitaxial strain. The onset superconducting transition temperature is up to 50 K, exceeding the McMillan limit, in the 1212 structure. Angle-resolved photoemission spectroscopy reveals key Fermi surface differences in these atomically-engineered structures. In superconducting 1212 and 2222 films, a dispersive hole-like band (i.e. the {\gamma} band) crosses the Fermi level, surrounding the Brillouin zone corner. In contrast, the top of the {\gamma} flat band is observed ~70 meV below the Fermi level in the non-superconducting 1313 films. Our findings expand the family of ambient-pressure nickelate superconductors and establish a connection between structural configuration, electronic structure, and the emergence of superconductivity in nickelates.