Signatures of superconductivity near 80 K in a nickelate under high pressure

摘要

Signatures of superconductivity near 80 K in a nickelate under high pressure

材料

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方法

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关键词

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亮点

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结论

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主要论断

• Superconductivity is observed in La₃Ni₂O₇ single crystals under high pressure with onset T_c up to 80 K, above 14 GPa.
  • 证据: Resistance drops sharply at ≈80 K under 14-43.5 GPa,Zero resistance observed in hydrostatic conditions,AC susceptibility shows diamagnetic response below 77 K at 25.2 GPa
• The superconducting state emerges from a strange metal phase with linear temperature resistance up to 300 K.
  • 证据: Normal state resistance above T_c is linear in temperature (T-linear) from T_c to 300K
• The high-pressure Fmmm phase (Ni-O-Ni angle 180°) enables metallization of the interlayer dz2 σ-bonding bands, creating hole pockets around Γ and mimicking hole-doped bilayer cuprates.
  • 证据: DFT calculations show dz2 bonding bands cross Fermi level at 29.5 GPa,Fermi surface topology changes from AP to HP

研究流程

• crystal_growth — High-quality single crystals grown.
  • 材料: La₃Ni₂O₇ single crystals
  • 方法: Vertical optical-image floating-zone furnace; Oxygen pressure 15 bar; 5-kW Xe arc lamp
  • 观察: Metallic at ambient, Fermi liquid behavior
• high_pressure_electrical_transport — Superconductivity with onset T_c ≈80 K at pressures 14-43.5 GPa.
  • 材料: La₃Ni₂O₇ single crystal (≈80×60×10 µm³)
  • 方法: Four-probe resistance in diamond anvil cell; Pressure medium: cBN+epoxy or KBr; PPMS for temperature and field
  • 观察: At >14 GPa, resistance drop at ≈80 K indicative of superconductivity; Linear normal state resistance (strange metal); Zero-resistance flat stage in KBr medium
• magnetic_susceptibility — Diamagnetism confirms superconductivity.
  • 材料: La₃Ni₂O₇ powder
  • 方法: AC magnetic susceptibility in diamond anvil cell; Mutual induction technique
  • 观察: Diamagnetic response below 77 K at 25.2 GPa
• high_pressure_synchrotron_xrd — Structural phase transition associated with superconductivity.
  • 材料: Powdered La₃Ni₂O₇
  • 方法: Synchrotron XRD at Beijing Synchrotron Radiation Facility; Rietveld refinement
  • 观察: Structural transition from Amam to Fmmm around 10 GPa; Ni-O-Ni angle reaches 180° in Fmmm phase
• dft_calculations — Metallization of interlayer σ-bonding bands enables high-T_c superconductivity.
  • 材料: Crystal structures at 1.6 and 29.5 GPa
  • 方法: DFT+U (U=4 eV) using VASP; Projector augmented-wave method
  • 观察: At₂₉.5 GPa: dz2 bonding bands cross Fermi level, forming small hole pocket; Fermi surface similar to hole-doped bilayer cuprates