Multiband Metallic Ground State in Multilayered Nickelates La₃Ni₂O₇ and La₄Ni₃O₁₀ Probed by 139La-NMR at Ambient Pressure

摘要

We report a 139La-NMR study of polycrystalline samples of multi(n)-layered nickelates, La₃Ni₂O₇−δ (n = 2) and La₄Ni₃O₁₀−δ (n = 3), at ambient pressure. Measurements of the nuclear magnetic resonance (NMR) spectra and nuclear spin relaxation rate (1/T₁) indicate the emergence of a density wave order with a gap below T* ∼ 150 K for La₃Ni₂O₇−δ and ∼130 K for La₄Ni₃O₁₀−δ. The finite value of 1/T₁ below T* indicates metallic ground states with the remaining density of states at the Fermi level (EF) under the density wave order. These features are attributed to multiple d electron bands with different characteristics. Above T*, the gradual decrease in 1/T₁T upon cooling implies the presence of a band with flat dispersion near EF. From our microscopic probes, we point out that these nickelates (n = 2 and 3) possess similar electronic states despite the difference in the formal valence of the Ni d electron states, which provides a basis for understanding the novel high-T_c superconductivity under high pressures.

材料

• La₃Ni₂O₇-δ
• La₄Ni₃O₁₀-δ

方法

• 139La nuclear magnetic resonance (NMR)

关键词

• density wave order
• multiband
• flat dispersion
• spin lattice relaxation rate

亮点

• The gradual decrease in 1/T₁T above T* suggests the presence of a band with flat dispersion near EF.

结论

• A density wave order with a gap opens below T* ≈150 K for La₃Ni₂O₇-δ and ≈130 K for La₄Ni₃O₁₀-δ.
• The finite 1/T₁ below T* indicates metallic ground states with remaining density of states at the Fermi level due to multiple d electron bands.
• Both nickelates exhibit similar electronic states despite different formal Ni valence.

主要论断

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研究流程

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