Angle-resolved photoemission spectroscopy of superconducting (La,Pr)3Ni2O7/SrLaAlO4 heterostructures

Liming Peng(Southern University of Science and Technology), Guangdi Zhou(Southern University of Science and Technology), Wei Lv(Southern University of Science and Technology), Yueying Li(Southern University of Science and Technology), Changming Yue(Southern University of Science and Technology), Haoliang Huang(Southern University of Science and Technology), Lizhi Xu(Southern University of Science and Technology), Jianchang Shen(University of Science and Technology of China), Yu Miao(University of Science and Technology of China), Wenhua Song(Southern University of Science and Technology), Zihao Nie(Southern University of Science and Technology), Yaqi Chen(Southern University of Science and Technology), Heng Wang(Southern University of Science and Technology), Weiqiang Chen(Southern University of Science and Technology), Yaobo Huang(Shanghai Advanced Research Institute), Zhen-Hua Chen(Southern University of Science and Technology), Tian Qian(Chinese Academy of Sciences), Junhao Lin(Southern University of Science and Technology), Junfeng He(University of Science and Technology of China), Yujie Sun(Southern University of Science and Technology), Zhuoyu Chen(Southern University of Science and Technology), Qi Xue(Southern University of Science and Technology)
National Science Review
May 21, 2025
10.1093/nsr/nwaf205
Cited by 44Open Access
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Abstract

ABSTRACT Ruddlesden-Popper bilayer nickelate thin film superconductors discovered under ambient pressure enable great possibilities for investigating electronic structures of the superconducting state. Here, we report angle-resolved photoemission spectroscopy (ARPES) measurements of 1, 2, and 3 unit-cell epitaxial La2.85Pr0.15Ni2O7 films grown on SrLaAlO4 substrates, through pure-oxygen in situ sample transportation. Evidence obtained using photons with distinct probing depths shows that conduction is localized primarily at the first unit cell near the interface. Scanning transmission electron microscopy (STEM), together with energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), indicates that interfacial Sr diffusion and pronounced p-d hybridization gradient may collectively account for the interfacial confinement of conduction. Fermi surface maps reveal hole doping compared to non-superconducting ambient-pressure bulk crystals. Measurements of dispersive band structures suggest contributions from both Ni dx2-y2 and dz2 orbitals at the Fermi level. Density functional theory (DFT) + U calculations capture qualitative features of the ARPES results, consistent with a hole-doped scenario. These findings constrain theoretical models of the superconducting mechanism and suggest potential for enhancing superconductivity in nickelates under ambient pressure.

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