[Paper Review] Progress of ambient-pressure superconductivity in bilayer nickelate thin films

Wenyuan Qiu, Dao-Xin Yao|arXiv (Cornell University)|Mar 11, 2026

Magnetic and transport properties of perovskites and related materials0 citations

TL;DR

The paper reviews ambient-pressure superconductivity in bilayer La3Ni2O7 thin films achieved via compressive epitaxial strain, discusses ARPES-detected Fermi surfaces, Tc enhancement strategies, and theory on pairing symmetry.

ABSTRACT

This review summarizes recent progress of ambient-pressure superconductivity in bilayer nickelate La$_3$Ni$_2$O$_7$ thin films, a major advancement following the discovery of high-pressure superconductivity in bulk La$_3$Ni$_2$O$_7$. First, we explain how epitaxial strain engineering enables ambient-pressure superconductivity in La$_3$Ni$_2$O$_7$ thin films, with compressive strain from substrates like SrLaAlO$_4$ stabilizing superconductivity. Next, we review experimental characterizations of related systems, with particular emphasis on ARPES measurements that have shown conflicting Fermi surface topologies. We then discuss progress in increasing the superconducting transition temperature $T_c$. Finally, we summarize theoretical studies of the electronic structure and pairing symmetry of La$_3$Ni$_2$O$_7$ thin films. Together, these advances establish bilayer nickelate thin films as a highly tunable and promising platform for exploring high-$T_c$ superconductivity.

Motivation & Objective

• Explain how epitaxial strain enables ambient-pressure superconductivity in La3Ni2O7 thin films.
• Review experimental characterizations, especially ARPES, and FS topologies linked to superconductivity.
• Survey methods that raise Tc in bilayer nickelate thin films.
• Summarize theoretical models of electronic structure and pairing symmetry in these films.

Proposed method

• Describe strain engineering as a route to stabilize the high-pressure-like phase at ambient pressure.
• Summarize growth techniques (PLD, GAE) and substrate choices (SrLaAlO4) that induce compressive strain.
• Discuss XAS/STEM/ARPES evidence for mixed Ni valence and 180° apical Ni–O–Ni angles.
• Review ARPES-identified Fermi-surface pockets (alpha, beta, gamma) and superconducting gaps.
• Summarize theoretical approaches (DFT, DMFT, cRPA, RPA, FRG, RMFT) used to understand electronic structure and pairing.
• Highlight proposed pairing symmetries (s±, etc.) and their dependence on FS topology.

Experimental results

Research questions

• RQ1 What is the role of the gamma pocket in enabling ambient-pressure superconductivity in bilayer nickelates?
• RQ2 How does substrate-induced compressive strain and the c/a lattice ratio affect Tc in La3Ni2O7 thin films compared to the bulk?
• RQ3 What is the likely pairing symmetry in these strained bilayer nickelate films, and how does it relate to Fermi-surface topology?
• RQ4 Which growth and interfacial engineering strategies most effectively raise Tc at ambient pressure?
• RQ5 How do theoretical models reconcile different ARPES observations and predict Tc and gap structures?

Key findings

• Ambient-pressure superconductivity with Tc exceeding 40 K is observed in La3Ni2O7 thin films under compressive strain on SrLaAlO4 substrates.
• Compressively strained films show superconducting transitions and zero resistance signatures unlike mildly compressive or tensile-strained films.
• ARPES reveals multiple Fermi-surface pockets (alpha, beta, gamma) in some films, while other films lack the gamma pocket, suggesting topology–SC links.
• STM reports a two-gap structure and a tendency toward anisotropic s-wave or s±-like pairing.
• Theoretical studies (DFT/DMFT, RPA/FRG, RMFT) support s±-type pairing scenarios and highlight sensitivity of pairing to FS details, with Tc potentially reaching ~60 K in mean-field estimates under favorable conditions.
• Recent work shows Tc onsets up to ~60 K in certain thin-film configurations and suggests that gamma-pocket presence correlates with superconductivity in some samples.