Spin-density-wave transition in monolayer-trilayer La₃Ni₂O₇ single crystals

摘要

本研究成功合成了高质量的长程有序杂化1313型La₃Ni₂O₇单晶（交替单层-三层结构），并对其物理性质进行了系统表征。在常压下，该材料呈现典型的半导体行为，并在170 K处出现明显的电阻率、磁化率和比热异常。¹³⁹La核磁共振谱明确证实该异常源于自旋密度波（SDW）相变。高压电输运测量表明，施加压力可以诱导金属化，但在高达65 GPa的压力下未观察到超导电性。这些发现将杂化1313型La₃Ni₂O₇确立为Ruddlesden-Popper镍酸盐家族中具有独特SDW转变的新成员，为研究杂化镍酸盐中晶体结构、电子序和超导电性之间的相互作用提供了新的平台。

材料

• La₃Ni₂O₇
• 1313-type La₃Ni₂O₇

方法

• Optical floating zone growth
• Powder X-ray diffraction
• Single crystal XRD
• STEM
• EDS
• Electrical transport
• Magnetic susceptibility
• Heat capacity
• 139La NMR
• High-pressure transport
• magnetic susceptibility measurement
• specific heat measurement
• nuclear magnetic resonance (NMR) spectroscopy
• high-pressure electrical transport

关键词

• spin density wave transition
• hybrid 1313 type
• monolayer trilayer stacking
• semiconducting behavior
• pressure induced metallization
• spin density wave (sdw) transition
• anomaly at 170 k
• metallization under pressure

亮点

• These findings establish hybrid 1313-type La₃Ni₂O₇ as a new member of the Ruddlesden-Popper nickelate family featuring a unique SDW transition.
• Provides a platform for investigating the interplay among crystal structure, electronic order, and superconductivity in hybrid nickelates.
• First identification of SDW in 1313-type La₃Ni₂O₇, establishing it as a new member of RP nickelate family with distinct electronic order.

结论

• Hybrid 1313-type La₃Ni₂O₇ exhibits semiconducting behavior and displays distinct anomalies at 170 K in resistivity, magnetic susceptibility, and specific heat.
• 139La NMR unambiguously indicates a spin-density-wave transition occurring at 170 K.
• High-pressure electrical transport demonstrates pressure-induced metallization but no superconductivity is observed up to 65 GPa.
• 1313-type La₃Ni₂O₇ exhibits a spin-density-wave transition at 170 K at ambient pressure and becomes metallic under pressure, but no superconductivity is observed up to 65 GPa.

主要论断

• Hybrid 1313-type La₃Ni₂O₇ exhibits a spin-density-wave transition at approximately 170 K, confirmed by 139La NMR.
  • 证据: Abstract: '139La nuclear magnetic resonance spectroscopy unambiguously confirms that these anomalies originate from a spin-density wave transition'
• No superconductivity is observed up to 65 GPa, indicating that superconductivity near 80 K in La₃Ni₂O₇ originates from the bilayer (2222) phase.
  • 证据: Abstract: 'high-pressure electrical transport measurements… reveal no discernible traces of superconductivity up to 65 GPa' and Discussion: 'demonstrate the superconductivity near 80 K originates exclusively in bilayer (2222) La₃Ni₂O₇ phase'
• Hybrid 1313-type La₃Ni₂O₇ exhibits a spin-density-wave transition at 170 K.
  • 证据: NMR spectra show broadening and peak in 1/T₁T at 170 K; transport and specific heat also show anomaly at same temperature.
• No superconductivity is observed in the 1313 phase up to 65 GPa.
  • 证据: High-pressure resistance measurements up to 65 GPa show metallization but no zero-resistance or dropout indicating superconductivity.
• Superconductivity near 80 K in La₃Ni₂O₇ originates exclusively in the bilayer (2222) phase.
  • 证据: The pure 1313 phase does not show superconductivity, so the 80 K superconductivity in mixed samples must come from bilayer phase contamination.

研究流程

• Crystal growth
  • 材料: La₃Ni₂O₇-1313 single crystals
  • 方法: Optical floating zone method; Elevated oxygen pressures
  • 观察: High-quality, long-range ordered hybrid 1313-type structure; Phase purity confirmed by XRD and STEM
• Characterization
  • 材料: Single crystals
  • 方法: X-ray diffraction; Scanning transmission electron microscopy; Energy-dispersive X-ray spectroscopy
  • 观察: Cmmm space group with alternating monolayer-trilayer stacking; Ni-O-Ni angle 180°
• Physical property measurements — SDW transition at approximately 170K
  • 材料: Single crystals
  • 方法: Resistivity; Magnetic susceptibility; Heat capacity; 139La-NMR
  • 观察: Semiconducting behavior with anomaly at 170K; SDW transition confirmed by NMR
• High-pressure transport — Superconductivity near 80 K originates from bilayer (2222) phase, not 1313 phase
  • 材料: Single crystals
  • 方法: Electrical transport in diamond anvil cell; Helium and solid pressure media
  • 观察: Pressure-induced metallization but no superconductivity up to 65 GPa
• sample_growth — Successfully grew high-quality 1313 single crystals with no bilayer contamination.
  • 材料: La₂O₃; NiO; oxygen
  • 方法: optical floating zone method; elevated oxygen pressure
  • 观察: High-quality, phase-pure hybrid 1313-type La₃Ni₂O₇ single crystals
• structural_characterization — Crystals are phase-pure 1313 with fully ordered stacking.
  • 材料: single crystals
  • 方法: powder XRD; single crystal XRD; ABF-STEM; EDS; 139La NMR
  • 观察: Cmmm space group; Alternating monolayer-trilayer stacking; Long-range order; Three distinct La sites; No bilayer phase detected
• ambient_pressure_transport_and_thermodynamics — A density-wave transition occurs at 170 K.
  • 材料: single crystals
  • 方法: resistivity; magnetic susceptibility; heat capacity
  • 观察: Semiconducting behavior; Anomaly at 170 K in all three measurements; Magnetic susceptibility suppression near 170K; Heat capacity peak at 170K
• NMR_identification_of_SDW — The transition is a spin-density-wave transition at T_SDW ≈ 170 K.
  • 材料: single crystals
  • 方法: 139La NMR; NQR; temperature-dependent spectra
  • 观察: Broadening of NMR lines below 170K; Coexistence of paramagnetic and magnetic phases between 130-170K; Peak in 1/T₁T near 170K
• high_pressure_transport — Pressure induces metallization but no superconductivity in the 1313 phase.
  • 材料: single crystals; helium; cubic boron nitride
  • 方法: DAC; electrical transport
  • 观察: Suppression of semiconducting behavior; Metallization; No superconductivity up to 65 GPa