Re-entrant unconventional superconductivity induced by rare-earth substitution in Nd1-xEuxNiO2 thin films
High temperature superconductivity is typically associated with strong coupling and a large superconducting gap, yet these characteristics have not been demonstrated in the nickelates. Here, we provide experimental evidence that Eu substitution in the spacer layer of Nd<sub>1-x</sub>Eu<sub>x</sub>NiO<sub>2</sub> (NENO) thin films enhances the superconducting gap, driving the system toward a strong-coupling regime. This is accompanied by a magnetic-exchange-driven magnetic-field-enhanced superconductivity. We investigate the upper critical magnetic field, H<sub>c2</sub>, and the superconducting gap of superconducting NENO thin films with x = 0.2 to 0.35. Magnetoresistance measurements reveal magnetic-field-enhanced superconductivity in NENO films. We interpret this phenomenon as a result of an interaction between magnetic Eu ions and superconducting states in the Ni d<sub>x2-y2</sub> orbital. The upper critical magnetic field strongly violates the weak-coupling Pauli limit. Infrared spectroscopy confirms a large gap-to-T<sub>c</sub> ratio <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>2</mml:mn><mml:mi>Δ</mml:mi><mml:mo>/</mml:mo><mml:msub><mml:mrow><mml:mi>k</mml:mi></mml:mrow><mml:mrow><mml:mi>B</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub><mml:mo>≃</mml:mo><mml:mn>5</mml:mn><mml:mo>-</mml:mo><mml:mn>6</mml:mn></mml:math>, indicating a stronger coupling pairing mechanism in NENO relative to the Sr-doped NdNiO<sub>2</sub>. The substitution of Eu in the rare-earth layer causes pronounced modifications of the superconducting gap and magnetic interactions in Nd-based nickelates, opening new pathways to engineer high-T<sub>c</sub> superconductivity in infinite-layer nickelates.
Authors
- Sohrab Ismail‐Beigi (ORCID: https://orcid.org/0000-0002-7331-9624)
- A. Cavalleri (ORCID: https://orcid.org/0000-0002-3143-0850)
- Charles Ahn (ORCID: https://orcid.org/0000-0003-2921-0346)
- Rongting Wu (ORCID: https://orcid.org/0000-0003-2254-2591)
- Tiema Qian (ORCID: https://orcid.org/0000-0003-4673-5662)
- Hangoo Lee (ORCID: https://orcid.org/0000-0002-3437-1729)
- M. Buzzi (ORCID: https://orcid.org/0000-0001-7325-4632)
- D. Nicoletti (ORCID: https://orcid.org/0000-0001-7563-5252)
- A. V. Suslov (ORCID: https://orcid.org/0000-0002-2224-153X)
- Christopher A. Mizzi (ORCID: https://orcid.org/0000-0002-4209-854X)
- Cyprian Lewandowski (ORCID: https://orcid.org/0000-0002-6944-9805)
- Dmitry V. Chichinadze (ORCID: https://orcid.org/0000-0001-8713-4500)
- Boris Maiorov (ORCID: https://orcid.org/0000-0003-1885-0436)
- X. Yang
- Wenxin Li (ORCID: https://orcid.org/0000-0003-4329-4136)
- Wenzheng Wei
- Yu He (ORCID: https://orcid.org/0009-0001-8462-4229)
- Zheting Jin (ORCID: https://orcid.org/0000-0002-7532-4531)
- Frederick Walker
- D.T. Vu (ORCID: https://orcid.org/0000-0002-4508-1559)
Institutions
- Florida State University (US)
- Los Alamos National Laboratory (US)
- Yale University (US)
- University of Oxford (GB)
- National High Magnetic Field Laboratory (US)
- Max Planck Institute for the Structure and Dynamics of Matter (DE)
Publication Details
- Journal
- Nature Communications
- Published
- 2026-03-05
- DOI
- https://doi.org/10.1038/s41467-026-70254-0
- Primary Topic
- Magnetic and transport properties of perovskites and related materials
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- U.S. Department of Energy
- Yale University
- Florida State University
- National High Magnetic Field Laboratory
- Deutsche Forschungsgemeinschaft
- Office of Science
- U.S. Air Force
- Division of Materials Research
- Basic Energy Sciences
- High Magnetic Field Laboratory, Chinese Academy of Sciences