¹³⁹La nuclear quadrupole resonance studies of pressurized La₄Ni₃O₁₀

摘要

本文利用¹³⁹La核四极矩共振（NQR）技术，对单晶La₄Ni₃O₁₀在常压与2.3 GPa静水压下的密度波序进行了系统研究。结果表明，该材料的自旋密度波与电荷密度波相互交织，明显不同于La₃Ni₂O₇；约150 K时先出现短程密度波序，约139 K时发展为长程密度波序。施加压力后，短程和长程密度波序的转变温度分别以约1 K/GPa和10 K/GPa的速率降低，说明长程序受压力抑制更快。作者据此认为，自旋密度波和电荷密度波在La₄Ni₃O₁₀中均为超导态的竞争序，为理解密度波序与非传统超导的相互作用提供了新线索。

材料

• La₄Ni₃O₁₀
• La₃Ni₂O₇

方法

• 139La nuclear quadrupole resonance (NQR)
• high-pressure optical floating-zone technique
• magnetic susceptibility measurements using MPMS with VSM
• hydrostatic pressure up to 2.3 GPa using a piston-cylinder pressure cell
• 63Cu NQR pressure calibration
• spin-lattice relaxation time (T1) measurements
• stepped frequency-sweep NQR
• two-component Lorentzian-Gaussian fitting

关键词

• density wave orders
• spin density wave
• charge density wave
• intertwined sdw and cdw orders
• short range dw order
• long range dw order
• competing orders with superconductivity
• incommensurate dw order
• magnetic wipe out effect
• spin fluctuations
• unconventional superconductivity
• ruddlesden popper nickelates

亮点

• Spin and charge density-wave orders are found to be intertwined in La₄Ni₃O₁₀, in stark contrast to La₃Ni₂O₇.
• Short-range DW orders are observed near 150 K, well above the development of long-range DW orders at around 139 K.
• No peak splitting is observed in the NQR spectra at all temperatures, implying that the DW orders are incommensurate, unlike the commensurate DW order in La₃Ni₂O₇.
• A non-vanishing magnetic-quadrupolar coupling term manifests the intertwining of SDW and CDW orders.
• The La(2) site is capable of sensing the short-range CDW order that was proposed to appear first in the inner Ni-O layer.
• The decrease of the stretching exponent under pressure is much slower than at ambient pressure.
• The phase diagram shows a larger window of the short-range DW phase under pressure.

结论

• NQR measurements on the La(2) site of La₄Ni₃O₁₀ reveal successive short-range and long-range intertwined SDW and CDW orders at ambient pressure.
• Under a hydrostatic pressure up to 2.3 GPa, the intertwined DW orders appear to be suppressed simultaneously.
• The transition temperatures of the short-range and long-range DW orders decrease at rates of about 1 K/GPa and 10 K/GPa, respectively, so the long-range DW orders are suppressed much faster than the short-range orders.
• Compared to La₃Ni₂O₇, the intertwined DW orders in La₄Ni₃O₁₀ appear to compete more strongly with superconductivity.
• Both the spin density wave and charge density wave in La₄Ni₃O₁₀ are competing orders with the superconducting state.
• Pressure reduces the density of states near the Fermi level.

主要论断

• Spin density wave and charge density wave orders are intertwined in La₄Ni₃O₁₀, in contrast to La₃Ni₂O₇.
  • 证据: A non-vanishing magnetic-quadrupolar coupling term is observed.,The linewidth analysis reveals a negative covariance between quadrupolar and magnetic contributions.,No peak splitting is observed, indicating incommensurate DW orders.,The paper states that the phenomena differ remarkably from La₃Ni₂O₇ and provide compelling evidence for intertwining between SDW and CDW orders.
• Short-range density-wave order appears near 150 K, well above long-range density-wave order near 139 K.
  • 证据: Below 150 K, NQR line-shape broadening and asymmetry develop and spectra require a disordered-state Lorentzian plus ordered-state Gaussian decomposition.,The T1 data show a pronounced enhancement below 160 K and peak at about 139 K.,The abstract states short-range DW orders are observed near 150 K, above long-range DW orders around 139 K.
• Hydrostatic pressure suppresses long-range density-wave order much faster than short-range density-wave order.
  • 证据: Under 2.3 GPa, the long-range DW transition is suppressed to about 116 K.,The short-range characteristic temperature remains much closer to its ambient-pressure value.,The abstract and text report decrease rates of about 1 K/GPa for short-range order and about 10 K/GPa for long-range order.
• Both the spin density wave and charge density wave in La₄Ni₃O₁₀ are competing orders with the superconducting state.
  • 证据: The abstract states the results affirm both SDW and CDW as competing orders with the superconducting state.,The paper reports that intertwined DW orders are suppressed under pressure before superconductivity emerges in related nickelates.,The text states that enhanced competition between coexisting intertwined density waves and superconductivity in La₄Ni₃O₁₀ is probably a factor in the reduction of T_c.

研究流程

• sample_preparation — The measured La₄Ni₃O₁₀ crystals are suitable for microscopic NQR study of density-wave orders.
  • 材料: single-crystalline La₄Ni₃O₁₀; Cu₂O for pressure calibration
  • 方法: high-pressure optical floating-zone growth; magnetic susceptibility verification in MPMS with VSM option
  • 观察: High-quality single crystal was grown and verified; density-wave transition near 139 K agrees with literature.
• measurement — 139La NQR provides local probes of spin and charge degrees of freedom in pressurized La₄Ni₃O₁₀.
  • 材料: single-crystalline La₄Ni₃O₁₀; 139La nuclei at La(2) site
  • 方法: 139La nuclear quadrupole resonance (NQR); stepped frequency-sweep spectra; spin-lattice relaxation time T1 recovery fitting; piston-cylinder hydrostatic pressure cell
  • 观察: 139La(2) NQR spectra, resonance frequencies, line shapes, and T1 were recorded as functions of temperature and pressure.
• analysis — Spin and charge density-wave orders in La₄Ni₃O₁₀ are intertwined and develop through short-range order before long-range order.
  • 材料: 139La NQR spectra; resonance frequencies; linewidths; spin-lattice relaxation data
  • 方法: nuclear quadrupole Hamiltonian analysis; Lorentzian and Gaussian two-component fitting; Bayer-Kushida relation analysis; FWHM decomposition into quadrupolar and magnetic contributions; stretched exponential fitting of T1 recovery
  • 观察: Short-range DW onset near 150 K; long-range DW onset near 139 K; no peak splitting, indicating incommensurate order; T1 peaks near long-range transition; negative coupling term between CDW and SDW contributions.
• interpretation — The intertwined SDW and CDW orders in La₄Ni₃O₁₀ are competing orders with superconductivity and are suppressed by pressure at different rates.
  • 材料: temperature-dependent NQR results; ambient- and high-pressure data; comparison with La₃Ni₂O₇
  • 方法: construction of pressure-temperature phase diagram; comparison of transition suppression rates; comparison with prior transport and superconducting behavior
  • 观察: Long-range DW transition is suppressed from about 139 K to about 116 K under 2.3 GPa; short-range DW is suppressed much more slowly; suppression rates are about 10 K/GPa for long-range and about 1 K/GPa for short-range order.