Pressure-induced superconductivity in epitaxially-stabilized Pr₃Ni₂O₇ films

摘要

本研究通过外延稳定技术在LaAlO₃衬底上成功制备了Pr₃Ni₂O₇薄膜，突破了该化合物在块材中难以合成的热力学稳定性限制。常压下，无论是否经过臭氧退火处理，Pr₃Ni₂O₇薄膜均表现出绝缘行为；但在22 GPa的高压下，薄膜呈现出T线性的金属输运特性，并出现超导电性，起始超导转变温度（T_c onset）达66 K，零电阻温度约40 K。进一步研究发现，采用更小稀土离子Nd的Nd₃Ni₂O₇薄膜虽可被外延稳定，但在所测压力范围内未观察到超导。通过对La、Pr、Nd三种Ln₃Ni₂O₇薄膜的比较，发现超导所需的临界压力Pc随Ln离子半径减小而增大，这一趋势与块材中Ln替代的研究结果一致。该工作表明，外延稳定技术是拓展双层镍酸盐超导家族的有效手段，为探索新型超导材料提供了重要途径。

材料

• Pr₃Ni₂O₇
• Nd₃Ni₂O₇
• La₃Ni₂O₇

方法

• PLD
• XRD
• STEM
• high-pressure transport measurements

关键词

• superconductivity
• epitaxial stabilization
• chemical pressure
• pressure induced superconductivity

亮点

• First realization of Pr₃Ni₂O₇ phase and observation of pressure-induced superconductivity.
• Achieves T_c above that of La-based counterpart in thin films under similar pressure.
• Demonstrates that epitaxial stabilization overcomes thermodynamic instability for synthesizing new bilayer nickelates.

结论

• Pr₃Ni₂O₇ thin films, stabilized by epitaxy on LaAlO₃, exhibit insulating behavior at ambient pressure but show superconductivity with onset T_c of 66 K and zero resistance near 40 K at 22 GPa.
• Nd₃Ni₂O₇ films can also be stabilized but do not show superconductivity up to 20 GPa.
• Higher critical pressure Pc is required for smaller Ln ions, consistent with bulk Ln substitution trends.
• Epitaxial stabilization is a powerful technique to expand the family of superconducting bilayer nickelates.

主要论断

• Pr₃Ni₂O₇ thin films exhibit superconductivity with onset T_c66 K and zero resistance at 37 K under 22 GPa
  • 证据: From abstract: 'they show T-linear metallic transport and superconductivity reaching an onset T_c of 66 K and zero-resistance at nearly 40 K at 22 GPa'
• Critical pressure Pc increases with decreasing Ln ionic radius in Ln₃Ni₂O₇ films
  • 证据: From abstract: 'a higher Pc is required for smaller Ln ions, consistent with trends observed in bulk studies'

研究流程

• thin_film_deposition — Pr₃Ni₂O₇ thin film stabilized on LaAlO₃
  • 材料: LaAlO₃ substrate; Pr₃Ni₂O₇ target
  • 方法: pulsed-laser deposition
  • 观察: epitaxial Pr₃Ni₂O₇ film
• structural_characterization — Film is epitaxial with predominant bilayer stacking
  • 材料: Pr₃Ni₂O₇/LaAlO₃
  • 方法: X-ray diffraction; scanning transmission electron microscopy
  • 观察: crystal structure; bilayer stacking; strain state
• high_pressure_resistivity_measurements — Superconductivity emerges at 22 GPa with onset T_c66K
  • 材料: Pr₃Ni₂O₇ film on LaAlO₃
  • 方法: cubic-anvil cell; liquid pressure medium
  • 观察: resistivity vs temperature; superconducting transition