Source capture
Authors Meng Zhang, Xi Yan
arXiv / Publisher https://arxiv.org/abs/2605.11584
PDF https://arxiv.org/pdf/2605.11584
Relevance score 5.857
Primary category cond-mat.supr-con
Published 2026-05-13
Research paradigm Unknown
Sample form Thin Film

Summary

Bilayer Ruddlesden-Popper nickelates exhibit superconductivity near 80 K under high pressure, and recent work has stabilized RA3Ni2O7 (RA = rare earth or alkaline earth element) superconducting thin films at ambient pressure via epitaxial strain, enabling transport, spectroscopic, microscopic, and device measurements. This review summarizes experimental progress on ambient-pressure superconducting bilayer nickelate thin films, covering synthesis routes, oxygen stoichiometry, substrate-induced strain, normal-state transport, superconducting properties, doping phase diagrams, and momentum-resolved electronic structure. Key unresolved issues include the reproducibility of phase-pure ultrathin films, the microscopic origin of the two-step superconducting transition, the roles of oxygen defects and substrate doping, the position of the Ni 3dz2-derived γ band, and the pairing symmetry. The review concludes that future work must establish more quantitative links between crystal structure, orbital reconstruction, and superconductivity to deepen the understanding of this unconventional high-temperature superconducting system.

Materials

  • RA3Ni2O7 (RA = rare earth or alkaline earth)

Methods

  • PLD
  • Molecular beam epitaxy
  • Gigantic-oxidative atomic-layer-by-layer epitaxy
  • ARPES
  • Scanning tunneling microscopy/spectroscopy
  • Resonant inelastic X-ray scattering
  • Transport measurements

Keywords

Highlights

  • First comprehensive review of experimental progress on ambient-pressure superconducting bilayer nickelate films.
  • Identifies critical challenges and outlines experimental directions for establishing quantitative structure-property relationships.

Conclusions

  • Key unresolved issues include the reproducibility of phase-pure ultrathin films, the microscopic origin of the two-step superconducting transition, the role of oxygen defects and substrate-derived doping, the position of the Ni 3dz2-derived γ band, and the pairing symmetry.
  • Future work must establish more quantitative links between crystal structure, orbital reconstruction, and superconductivity.

Main claims

  • Ambient-pressure superconducting bilayer nickelate films have been realized via compressive epitaxial strain, enabling spectroscopic and device measurements.
    • Evidence: Review of multiple experimental reports: Ko et al. 2025, Zhou et al. 2025, etc.
  • Key unresolved issues include reproducibility of ultrathin films, origin of two-step transition, role of oxygen defects and substrate doping, position of γ band, and pairing symmetry.
    • Evidence: Discussion of conflicting ARPES results on γ band position; need for oxygen control; granular superconductivity interpretation

Workflow

Not available in this batch.