Strong oxidizing annealing of bilayer La₃Ni₂O₇-δ results in suppression of superconductivity under high pressure

摘要

The discovery of superconductivity with an onset temperature of ∼80 K in pressurized bilayer Ruddlesden-Popper La₃Ni₂O₇-δ has attracted much attention. Despite intense research, determination of the exact oxygen content and understanding of the relationship between superconductivity and oxygen content remain a big challenge. Here, we report a systematical study on the structure and physical properties of La₃Ni₂O₇-δ polycrystalline powders which were prepared using the sol-gel method at ambient pressure and then annealed under high oxygen pressure (pO₂) or in ozone. The superconducting transition of La₃Ni₂O₇-δ at ∼80 K under high pressure is suppressed for high pO₂ and ozone annealed samples. We attribute this to the combination of the following two reasons: (i) damage of the bilayer structure, as revealed by powder X-ray diffraction, scanning transmission electron microscopy and pair distribution function measurements, and (ii) hole overdoping due to the increasing of oxygen content. Our results reveal that the bilayer structure in La₃Ni₂O₇-δ is fragile and post-annealing under mild oxidization is suitable for maintaining the integrity of the bilayer structure and increasing oxygen content.

材料

• La₃Ni₂O₇-δ polycrystalline powders

方法

• sol-gel method
• X-ray diffraction
• STEM
• pair distribution function measurements

关键词

• oxygen content
• hole overdoping
• bilayer structure fragility
• superconductivity suppression

亮点

• Strong oxidizing annealing of bilayer La₃Ni₂O₇-δ results in suppression of superconductivity under high pressure.
• Reveals fragility of bilayer structure and relationship with oxygen content.

结论

• Superconducting transition of La₃Ni₂O₇-δ at ≈80 K under high pressure is suppressed for high pO₂ and ozone annealed samples.
• This suppression is attributed to damage of the bilayer structure and hole overdoping due to increasing oxygen content.
• Bilayer structure in La₃Ni₂O₇-δ is fragile and post-annealing under mild oxidization is suitable for maintaining integrity and increasing oxygen content.

主要论断

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研究流程

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