Re-entrant unconventional superconductivity induced by rare-earth substitution in Nd 1- x Eu x NiO 2 thin films

Journal article

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 Nd1-xEuxNiO2 (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, Hc2, 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 dx2-y2 orbital. The upper critical magnetic field strongly violates the weak-coupling Pauli limit. Infrared spectroscopy confirms a large gap-to-Tc ratio 2Δ/kBTc≃5−6, indicating a stronger coupling pairing mechanism in NENO relative to the Sr-doped NdNiO2. 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-Tc superconductivity in infinite-layer nickelates.

Authors: Vu, D; Lee, H; Nicoletti, D; Wei, W; Jin, Z

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Nature Research
• Journal: Nature Communications
• Volume: 17
• Issue: 1
• Article number: 3480
• Publication date: 2026-03-05
• Acceptance date: 2026-02-20
• DOI: 10.1038/s41467-026-70254-0
• EISSN: 2041-1723
• ISSN: 2041-1723
• Language: English
• Keywords: Superconductivity; Thin film; Pairing; Magnetoresistance; Critical field; Pauli exclusion principle; Coupling (piping); Proximity effect (electron beam lithography)