Bulk superconductivity up to 96 K in pressurized nickelate single crystals.
basic_science · Level V
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- Record sourced from PubMed, PMID 41331351.
- Also identified by DOI 10.1038/s41586-025-09954-4.
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Abstract
Recently, the Ruddlesden-Popper bilayer nickelate La<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> has emerged as a superconductor with a transition temperature (T<sub>c</sub>) of approximately 80 K above 14 GPa (refs. <sup>1-3</sup>). Achieving a higher T<sub>c</sub> in nickelate superconductors, along with the synthesis of reproducible high-quality single crystals without relying on high-oxygen-pressure growth conditions, remains a significant challenge<sup>4-7</sup>. Here we report superconductivity up to 96 K under high pressure in bilayer nickelate single crystals synthesized at ambient pressure. Energy-dispersive spectroscopy, single-crystal X-ray diffraction, nuclear quadrupole resonance and scanning transmission electron microscopy evidenced high crystal quality of the flux-grown La<sub>2</sub>SmNi<sub>2</sub>O<sub>7-δ</sub> single crystals. La<sub>2</sub>SmNi<sub>2</sub>O<sub>7</sub> exhibits clear bulk superconductivity, including zero resistivity ( <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>T</mi></mrow> <mrow><mi>c</mi> <mo>,</mo> <mi>max</mi></mrow> <mrow><mi>onset</mi></mrow> </msubsup> </math> = 92 K and <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>T</mi></mrow> <mrow><mi>c</mi> <mo>,</mo> <mi>max</mi></mrow> <mrow><mi>zero</mi></mrow> </msubsup> </math> = 73 K at 21.6 GPa) and the Meissner effect (T<sub>c</sub> = 60 K at 20.6 GPa). A low-temperature high-pressure structural study indicates that both monoclinic and tetragonal structures can support superconductivity in this bilayer nickelate. Furthermore, we established a correlation between higher T<sub>c</sub> under high pressures and larger in-plane lattice distortion under ambient conditions, corroborated by observing even higher <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>T</mi></mrow> <mrow><mi>c</mi></mrow> <mrow><mi>onset</mi></mrow> </msubsup> </math> of 96 K in La<sub>1.57</sub>Sm<sub>1.43</sub>Ni<sub>2</sub>O<sub>7-δ</sub>. This study overcomes key limitations in growing nickelate superconductor crystals, resolves the crystal structure in the superconducting state and demonstrates an effective pathway towards achieving higher T<sub>c</sub>.