Superconducting Lanthanum Nickel Oxides with Bilayered and Trilayered Crystal Structures

Summary

In₂₀₂₃, the bilayer nickel oxide La₃Ni₂O₇ was discovered to exhibit superconductivity at a pressure of approximately 14 GPa with a critical temperature near 80 K, featuring a structure similar to that of high-temperature copper oxides; subsequently, superconductivity was also found in the trilayer compound La₄Ni₃O₁₀. These two compounds belong to the Ruddlesden–Popper phase, which consists of alternating stacks of NiO₂ square-lattice layers and LaO rock-salt layers. Current research is mainly pursued along three directions: expanding the chemical diversity of the compounds, raising the superconducting transition temperature through elemental substitution, and elucidating the pairing mechanism of superconductivity. However, key experiments must be conducted under high pressure, which poses difficulties for mechanistic studies; therefore, developing nickel oxides that exhibit superconductivity at lower pressures or even ambient pressure is of great significance. This review summarizes the existing knowledge of these systems, highlights the relatively mature methods for sample synthesis and characterization, and briefly outlines their electronic properties, aiming to provide a foundation for future material exploration and physical understanding of the underlying mechanisms.

Materials

• La₃Ni₂O₇
• La₄Ni₃O₁₀
• La₂NiO₄
• LaNiO₃
• La₅Ni₃O₁₁
• La₃Ni₂O₆

Methods

Not available in this batch.

Keywords

• ruddlesden popper phases
• nickelate superconductors
• high pressure superconductivity
• oxygen stoichiometry
• sample synthesis

Highlights

• This review summarizes the present state of knowledge on superconducting lanthanum nickel oxides with bilayered and trilayered crystal structures.
• It emphasizes the importance of sample synthesis and characterization for progress in unconventional superconductors.

Conclusions

• Superconductivity in La₃Ni₂O₇ and La₄Ni₃O₁₀ is likely unconventional and rooted in their unique electronic structures.
• Ke_y experiments must be performed under high pressure, posing difficulties for mechanistic studies.
• Developing nickel oxides that exhibit superconductivity at lower pressures is of great significance.
• Sample synthesis and characterization are already well established and often decisive for progress.

Main claims

• La₃Ni₂O₇ exhibits superconductivity under high pressure above 14 GPa with T_c up to 80 K.
  • Evidence: Abstract,Full text: La₃Ni₂O₇ was discovered to exhibit superconductivity under pressures above approximately 14 GPa, with transition temperature reaching nearly 80 K.
• Superconductivity occurs in the tetragonal phase of the RP structure.
  • Evidence: Full text,Section 2.2: Superconductivity occurs in the tetragonal phase, the ideal structure of the RP phase.
• Oxygen stoichiometry strongly affects superconductivity; excess oxygen and oxygen deficiency have different effects in La₃Ni₂O₇ and La₄Ni₃O₁₀.
  • Evidence: Full text,Section 4.3.2: In La₃Ni₂O₇, oxygen excess shifts superconductivity to higher pressures and reduces T_c; in La₄Ni₃O₁₀, oxygen deficiency shifts superconductivity to higher pressures and lowers maximum T_c.

Workflow

Not available in this batch.