Nodeless superconducting gap and electron-boson coupling in (La,Pr,Sm) 3 Ni 2 O 7 films
- Jianchang Shen
- Guangdi Zhou
- Yu Miao
- Peng Li
- Zhipeng Ou
- Yaqi Chen
- Zechao Wang
- Runqing Luan
- Hongxu Sun
- Zikun Feng
- Xinru Yong
- Yueying Li
- Lizhi Xu
- Wei Lv
- Zihao Nie
- Heng Wang
- Haoliang Huang
- Yu-Jie Sun
- Qi-Kun Xue
- Junfeng He
- Zhuoyu Chen
2026-05-21
The discovery of superconductivity in Ruddlesden-Popper (RP) bilayer nickelate films under ambient pressure provides an opportunity to directly investigate electronic energy scales of the superconducting state and the pairing mechanism. We report angle-resolved photoemission spectroscopy measurements of superconducting (La,Pr,Sm) 3 Ni 2 O 7 thin films by developing an ultra-high vacuum cryogenic sample quenching and transfer technique. A superconducting gap of ~18 meV with coherence peaks is observed along the Brillouin zone diagonal. The finite gap persists across the entire Brillouin zone, revealing the absence of gap nodes. A kink is observed in the energy-momentum dispersion at ~70 meV below Fermi level, indicating an electron-boson coupling. The simultaneous observation of a nodeless superconducting gap and electron-boson coupling provides insight into the pairing symmetry and gluing mechanism in RP bilayer nickelates.