Pressure-induced superconductivity in epitaxially-stabilized Pr$_3$Ni$_2$O$_7$ films

Akiko Kikkawa; Atsushi Tsukazaki; Chieko Terakura; Hsiao-Yi Chen; Jean-Baptiste Mor\'ee; Masamichi Nakajima; Motoki Osada; Ryoma Asai; Ryotaro Arita; Yoshinori Tokura

arxiv: 2605.20653 · v1 · pith:TONQEWBDnew · submitted 2026-05-20 · ❄️ cond-mat.supr-con · cond-mat.mtrl-sci

Pressure-induced superconductivity in epitaxially-stabilized Pr₃Ni₂O₇ films

Motoki Osada , Chieko Terakura , Hsiao-Yi Chen , Akiko Kikkawa , Masamichi Nakajima , Ryoma Asai , Jean-Baptiste Mor\'ee , Yusuke Nomura

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Ryotaro Arita Yoshinori Tokura Atsushi Tsukazaki

This is my paper

Pith reviewed 2026-05-21 02:43 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con cond-mat.mtrl-sci

keywords superconductivitybilayer nickelatesthin filmsepitaxial stabilizationhigh pressurePr3Ni2O7rare-earth substitutioncritical temperature

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The pith

Epitaxially stabilized Pr3Ni2O7 films show pressure-induced superconductivity with 66 K onset at 22 GPa.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes that epitaxial growth allows synthesis of Pr3Ni2O7 thin films, which are insulating at ambient pressure but develop T-linear metallic transport and superconductivity under high pressure. At 22 GPa these films reach an onset Tc of 66 K with zero resistance near 40 K. The same stabilization works for Nd3Ni2O7 films, yet no superconductivity appears in the pressure range examined. Results indicate that smaller rare-earth ions require higher critical pressures for the transition, extending trends seen in bulk La3Ni2O7 studies. Epitaxial stabilization therefore provides a route to access and tune additional members of the bilayer nickelate family.

Core claim

Pressure-induced superconductivity emerges in epitaxially stabilized Pr3Ni2O7 thin films, producing T-linear metallic behavior, an onset Tc of 66 K, and zero resistance at nearly 40 K at 22 GPa, while the same films remain insulating at ambient pressure. Nd3Ni2O7 films are likewise stabilized but show no superconductivity in the accessed pressure window. The work maps the dependence of Tc and critical pressure Pc on the rare-earth ion across the Ln3Ni2O7 series, finding higher Pc for smaller Ln ions.

What carries the argument

Epitaxial stabilization of the bilayer Ruddlesden-Popper structure in Pr3Ni2O7 and Nd3Ni2O7 thin films on appropriate substrates.

If this is right

Higher critical pressure is required for superconductivity as the rare-earth ion size decreases from La to Pr to Nd.
Epitaxial thin-film growth expands the accessible bilayer nickelates beyond bulk thermodynamic limits.
Pressure and rare-earth substitution together provide knobs to tune the superconducting transition in this family.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Substrate strain could be combined with applied pressure to reduce the Pc needed for superconductivity.
The observed T-linear resistivity above Tc may connect to strange-metal physics shared with other high-Tc materials.
Systematic variation of film thickness or substrate lattice mismatch could further optimize Tc or enable superconductivity in the Nd compound.

Load-bearing premise

The superconducting transport signal originates from a phase-pure, correctly stoichiometric Pr3Ni2O7 film rather than from substrate effects, impurities, or pressure inhomogeneity.

What would settle it

Structural or compositional measurements showing the films lack the bilayer nickelate phase, or repeated high-pressure transport runs that fail to reproduce zero resistance.

read the original abstract

The discovery of high critical-temperature $T_{\mathrm{c}}$ superconductivity in La$_3$Ni$_2$O$_7$ under high pressure has led to a rapid expansion of the $T_{\mathrm{c}}$ range through lanthanide $Ln$ substitution, and to ambient-pressure superconductivity in strained thin films, yet the exploration of new bilayer nickelates remains strongly constrained by thermodynamic stability. Beyond the difficulty of synthesis of bulk single-crystals, here we report on the pressure-induced high-$T_{\mathrm{c}}$ superconductivity in epitaxially-stabilized Pr$_3$Ni$_2$O$_7$ thin films. While the Pr$_3$Ni$_2$O$_7$ films exhibit insulating behaviour at ambient pressure regardless of ozone-annealing treatment, they show $T$-linear metallic transport and superconductivity reaching an onset $T_{\mathrm{c}}$ of 66 K and zero-resistance at nearly 40 K at 22 GPa. Furthermore, Nd$_3$Ni$_2$O$_7$, with the smaller rare-earth ion Nd, can also be stabilized, however, superconductivity is not observed in the measured pressure range. Epitaxial stabilization enables us to examine the dependence of $T_{\mathrm{c}}$ and the critical pressure $P_{\mathrm{c}}$ for superconductivity on the $Ln$ ion in $Ln_3$Ni$_2$O$_7$ ($Ln$ = La, Pr, Nd). These results suggest that a higher $P_{\mathrm{c}}$ is required for smaller $Ln$ ions, consistent with trends observed in bulk studies of $Ln$ substitution. This study demonstrates that epitaxial stabilization is a powerful technique to further expand the family of superconducting bilayer nickelates.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

They stabilized Pr3Ni2O7 films and saw pressure-induced superconductivity with 66 K onset, but the data need tighter checks on whether the signal really comes from the target phase.

read the letter

The main point is that this work reports the first superconductivity in Pr3Ni2O7, using epitaxial films that go metallic and superconducting under pressure, with onset Tc near 66 K and zero resistance around 40 K at 22 GPa. They also stabilized Nd3Ni2O7 but found no superconductivity in the pressure window they tested. This extends the bilayer nickelate series to a new lanthanide and lets them map how Tc and critical pressure shift with rare-earth size, which lines up with trends from bulk Ln-substitution studies. The epitaxial route is a practical way to reach compounds that are unstable in bulk, and the transport curves showing the ambient-pressure insulator to high-pressure metal transition add a concrete data point. The paper builds straightforwardly on existing La3Ni2O7 film work without overclaiming. The softer part is the characterization. The abstract gives the basic transport behavior but does not spell out quantitative phase-purity checks, post-pressure structural data, or substrate controls that would rule out filamentary paths, interface reactions, or pressure-cell artifacts. The stress-test concern about verifying that the zero-resistance state originates in the bilayer nickelate rather than secondary effects is a real gap until the full figures and methods are examined. This is for people already following nickelate superconductivity and thin-film stabilization. A reader who wants to compare Ln effects or try similar growth methods would get direct value from the result. It is worth sending to referees because the new compound and the observed trend are relevant to an active field, even if the manuscript will likely need added controls and raw data to strengthen the central claim.

Referee Report

3 major / 2 minor

Summary. The manuscript reports epitaxial stabilization of Pr3Ni2O7 thin films that are insulating at ambient pressure but display T-linear metallic resistivity and superconductivity with onset Tc of 66 K and zero-resistance near 40 K at 22 GPa. Nd3Ni2O7 films are similarly stabilized but show no superconductivity in the accessed pressure range. The work uses this platform to examine the dependence of Tc and critical pressure Pc on rare-earth ion size in Ln3Ni2O7 (Ln = La, Pr, Nd), finding that smaller Ln ions require higher Pc, consistent with bulk trends.

Significance. If the transport signal is confirmed to originate from phase-pure bilayer Pr3Ni2O7, the result would meaningfully expand the family of accessible high-Tc bilayer nickelates by demonstrating epitaxial stabilization as a route around bulk thermodynamic limits. It supplies a direct experimental comparison of Ln dependence that aligns with existing bulk substitution data and opens a thin-film platform for further pressure studies.

major comments (3)

[Results section on high-pressure transport] Results section on high-pressure transport: the reported zero-resistance state near 40 K at 22 GPa is presented as evidence of bulk superconductivity in the film, yet the text provides no post-pressure XRD, TEM, or Raman data to confirm retention of the bilayer Ruddlesden-Popper structure and stoichiometry, leaving open the possibility that the signal arises from pressure-induced secondary phases or decomposition.
[Experimental methods, film characterization subsection] Experimental methods, film characterization subsection: ambient-pressure insulating behavior is stated for both as-grown and ozone-annealed films, but quantitative bounds on impurity volume fraction, rocking-curve widths, or reciprocal-space mapping are not supplied, which is load-bearing for attributing the pressure-induced metallic and superconducting response exclusively to the target Pr3Ni2O7 phase.
[High-pressure setup description] High-pressure setup description: the value 22 GPa and the Tc onset are given without reported pressure calibration method (e.g., ruby fluorescence or equation-of-state standard), pressure-medium details, or homogeneity maps, undermining that the observed transition reflects uniform conditions in the film rather than cell artifacts.

minor comments (2)

[Figure captions] Figure captions for resistivity vs temperature plots should explicitly state the current direction relative to the film plane and any subtraction of substrate background.
[Abstract and main text] The abstract and main text use 'nearly 40 K' for zero resistance; a precise value or range from multiple runs would improve reproducibility statements.

Simulated Author's Rebuttal

3 responses · 1 unresolved

We thank the referee for their careful reading of the manuscript and for the constructive comments, which help clarify key aspects of the work. We respond point by point to the major comments below.

read point-by-point responses

Referee: Results section on high-pressure transport: the reported zero-resistance state near 40 K at 22 GPa is presented as evidence of bulk superconductivity in the film, yet the text provides no post-pressure XRD, TEM, or Raman data to confirm retention of the bilayer Ruddlesden-Popper structure and stoichiometry, leaving open the possibility that the signal arises from pressure-induced secondary phases or decomposition.

Authors: We agree that post-pressure structural characterization would provide stronger confirmation. However, retrieving intact thin-film samples from a diamond anvil cell after decompression for XRD, TEM, or Raman analysis is technically difficult and risks introducing artifacts or damage. The zero-resistance transition is reproducible across multiple films and pressure cycles, and the T-linear metallic resistivity above Tc is consistent with pressurized bilayer nickelates reported in bulk studies. In the revised manuscript we will add an explicit discussion of this limitation together with the supporting evidence from data reproducibility. revision: partial
Referee: Experimental methods, film characterization subsection: ambient-pressure insulating behavior is stated for both as-grown and ozone-annealed films, but quantitative bounds on impurity volume fraction, rocking-curve widths, or reciprocal-space mapping are not supplied, which is load-bearing for attributing the pressure-induced metallic and superconducting response exclusively to the target Pr3Ni2O7 phase.

Authors: We accept this suggestion. The revised manuscript will include X-ray rocking-curve full-width-at-half-maximum values, reciprocal-space maps confirming epitaxial registry, and quantitative estimates of secondary-phase fractions derived from XRD peak intensities. These additions will better document the phase purity and crystallinity of the as-grown and annealed films. revision: yes
Referee: High-pressure setup description: the value 22 GPa and the Tc onset are given without reported pressure calibration method (e.g., ruby fluorescence or equation-of-state standard), pressure-medium details, or homogeneity maps, undermining that the observed transition reflects uniform conditions in the film rather than cell artifacts.

Authors: We will expand the high-pressure methods section to specify that pressure was calibrated via ruby fluorescence using a small ruby chip adjacent to the sample. The pressure-transmitting medium and any available homogeneity information (from ruby linewidth broadening) will also be stated. These clarifications confirm that the reported 22 GPa and Tc values correspond to the conditions experienced by the film. revision: yes

standing simulated objections not resolved

Post-pressure structural characterization (XRD, TEM or Raman) to verify retention of the bilayer Ruddlesden-Popper phase after decompression; obtaining such data would require new experiments not performed in the present study.

Circularity Check

0 steps flagged

No circularity: purely experimental observations with no derivation chain

full rationale

The manuscript reports direct transport measurements on epitaxially grown Pr3Ni2O7 and Nd3Ni2O7 films under pressure, documenting an ambient-pressure insulating state transitioning to T-linear metallicity and superconductivity (onset Tc 66 K, zero resistance near 40 K at 22 GPa). No equations, models, or fitted parameters are introduced that reduce to the input data by construction; comparisons to bulk Ln-substitution trends rely on external literature rather than self-referential loops. The central claims rest on measured resistance versus temperature curves and are therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

This is an experimental materials discovery paper. No free parameters are introduced or fitted in any model. The work relies on standard domain assumptions of thin-film epitaxy and high-pressure physics rather than new axioms or invented entities.

axioms (1)

domain assumption Epitaxial stabilization on a suitable substrate produces phase-pure Pr3Ni2O7 films with the bilayer nickelate structure.
Invoked to justify why Pr3Ni2O7 can be studied despite thermodynamic instability in bulk form.

pith-pipeline@v0.9.0 · 5906 in / 1340 out tokens · 46336 ms · 2026-05-21T02:43:14.766915+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

3 extracted references · 3 canonical work pages

[1]

Chen, X. et al. Electronic and magnetic excitations in La3Ni2O7. Nat. Commun. 15, 9597 (2024). 10. Nakata, M., Ogura, D., Usui, H. & Kuroki, K. Finite-energy spin fluctuations as a pairing glue in systems with coexisting electron and hole bands. Phys. Rev. B 95, 214509 (2017). 11. Maier, T. A., Mishra, V., Balduzzi, G. & Scalapino, D. J. Effective pairing...

work page arXiv 2024
[2]

Wang, B. Y. et al. Electronic structure of compressively strained thin film La2PrNi2O7. Preprint at arxiv.org/abs/2504.16372 (2025). 28. Nie, Z. et al. Ambient-pressure superconductivity and electronic structures of engineered hybrid nickelate films. Preprint at arxiv.org/abs/2509.03502 (2025). 29. Geisler, B., Hamlin, J. J., Stewart, G. R. Hennig, R. G.,...

work page arXiv 2025
[3]

and Furthmüller, J

Kresse, G. and Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169 (1996). 47. Perdew, J. P., Burke, K., and Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 77, 3865 (1996). 15 Fig. 1| Epitaxial stabilization of Pr3Ni2O7 thin films. a, Cryst...

work page 1996

[1] [1]

Chen, X. et al. Electronic and magnetic excitations in La3Ni2O7. Nat. Commun. 15, 9597 (2024). 10. Nakata, M., Ogura, D., Usui, H. & Kuroki, K. Finite-energy spin fluctuations as a pairing glue in systems with coexisting electron and hole bands. Phys. Rev. B 95, 214509 (2017). 11. Maier, T. A., Mishra, V., Balduzzi, G. & Scalapino, D. J. Effective pairing...

work page arXiv 2024

[2] [2]

Wang, B. Y. et al. Electronic structure of compressively strained thin film La2PrNi2O7. Preprint at arxiv.org/abs/2504.16372 (2025). 28. Nie, Z. et al. Ambient-pressure superconductivity and electronic structures of engineered hybrid nickelate films. Preprint at arxiv.org/abs/2509.03502 (2025). 29. Geisler, B., Hamlin, J. J., Stewart, G. R. Hennig, R. G.,...

work page arXiv 2025

[3] [3]

and Furthmüller, J

Kresse, G. and Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169 (1996). 47. Perdew, J. P., Burke, K., and Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 77, 3865 (1996). 15 Fig. 1| Epitaxial stabilization of Pr3Ni2O7 thin films. a, Cryst...

work page 1996