Re-entrant unconventional superconductivity induced by rare-earth substitution in Nd<sub>1-x</sub>Eu<sub>x</sub>NiO<sub>2</sub> thin films.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41786762.
- Also identified by DOI 10.1038/s41467-026-70254-0 and PMC identifier 13079897.
- Licence recorded as CC BY-NC-ND.
- Because redistribution is not established, this page shows the abstract only. Follow the links below for the full text.
Abstract
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 <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>2</mn> <mi>Δ</mi> <mo>/</mo> <msub><mrow><mi>k</mi></mrow> <mrow><mi>B</mi></mrow> </msub> <msub><mrow><mi>T</mi></mrow> <mrow><mi>c</mi></mrow> </msub> <mo>≃</mo> <mn>5</mn> <mo>-</mo> <mn>6</mn></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.