Density-wave order enhances the phonon thermal Hall effect in a trilayer nickelate

摘要

在三层Ruddlesden-Popper镍酸盐La₄Ni₃O₁₀的常压正常态中，研究人员观测到由密度波序增强的声子热霍尔效应。该材料在约140 K发生密度波相变，热霍尔响应在转变温度以下急剧增强，热霍尔角从160 K时的1.5‰升至100 K附近的6‰，并在70 K达到约7‰的峰值，同时在热霍尔电阻率上出现两个明显平台。纵向热导率几乎不随磁场变化且电子贡献极小，证明纵向与横向热输运均以声子为主。从热霍尔数据提取的特征能量约4.1 meV，与磁振子-声子色散交叉跨越能量3.2 meV高度吻合，表明自旋密度波序诱导的磁振子-声子杂化是增强热霍尔效应的核心机制。该工作揭示了镍酸盐中自旋-晶格耦合对声子输运的显著调控，并指出这种动态耦合可能通过软化光学声子参与压制反铁磁序、促进高压下超导电性的出现，为理解非常规超导体中电荷、自旋与晶格自由度的交织提供了新视角。

材料

• La₄Ni₃O₁₀

方法

• Thermal Hall effect measurement
• Longitudinal thermal conductivity measurement
• Electrical resistivity measurement
• Magnetoresistance measurement
• Wiedemann-Franz law analysis

关键词

• thermal hall effect
• density wave order
• magnon phonon hybridization
• phonon transport
• spin lattice coupling

亮点

• We report the first observation of a finite phonon thermal Hall effect in the trilayer nickelate La₄Ni₃O₁₀ at ambient pressure.
• The thermal Hall angle reaches a maximum of nearly 7‰, approximately twice that in cuprates and three times that in SrTiO₃.
• The thermal Hall response is dramatically enhanced below the density-wave transition at ≈140 K, with two distinct plateaus in the thermal Hall resistivity.
• The characteristic energy scale from the thermal Hall response (≈4.1 meV) closely matches the magnon–phonon crossing span (≈3.2 meV), pointing to magnon–phonon hybridization as the primary enhancement mechanism.

结论

• In La₄Ni₃O₁₀, we observe an enhanced phonon thermal Hall effect tied to the density-wave transition.
• We propose that spin-lattice coupling (magnon-phonon hybridization) from SDW order drives both the thermal Hall enhancement and the suppression of long-range antiferromagnetism.
• Thus, La₄Ni₃O₁₀ exemplifies intertwined charge, spin, and lattice orders, where phonons dressed by electronic order play an active role in the normal state of superconducting nickelates.

主要论断

• A finite phonon thermal Hall effect is observed in La₄Ni₃O₁₀ at ambient pressure, strongly enhanced below the density-wave transition at ≈140 K.
  • 证据: κxy/κxx increases from 1.5‰ at 160 K to 6‰ at 100 K, peaks at ≈7‰ at 70 K,two distinct plateaus in thermal Hall resistivity below T*
• The thermal Hall signal is overwhelmingly phononic, not electronic.
  • 证据: κxx shows almost no magnetic field dependence at 0 T vs 10 T,electronic contribution estimated from Wiedemann-Franz law is one to two orders of magnitude smaller than measured κxy
• The characteristic energy scale of the enhanced thermal Hall effect (≈4.1 meV) matches the magnon–phonon crossing energy (≈3.2 meV), indicating magnon–phonon hybridization as the underlying mechanism.
  • 证据: fit of λxy gives T₀ = 48 K (4.1 meV),calculated phonon-magnon crossing span is 3.2 meV
• Magnon–phonon hybridization may also assist in destabilizing the spin-density-wave order under pressure and facilitate superconductivity.
  • 证据: speculative argument based on optical phonon softening under pressure,analogy to cuprates

研究流程

• measurement — A phononic thermal Hall effect is observed and strongly enhanced below the density-wave transition.
  • 材料: La₄Ni₃O₁₀ single crystals
  • 方法: resistivity; magnetoresistance up to 55T; longitudinal and transverse thermal conductivity in magnetic field; thermal Hall angle extraction
  • 观察: resistivity upturn and kink at ≈140 K indicating DW transition; thermal Hall angle κxy/κxx rises from 1.5‰ at 160 K to 6‰ at 100 K, peaks ≈7‰ at 70K; two plateaus in thermal Hall resistivity λxy; κxx nearly field-independent, electronic κxy contribution negligible
• analysis — The extracted characteristic energy matches the magnon–phonon crossing energy, pointing to magnon–phonon hybridization as the origin of the enhanced thermal Hall effect.
  • 方法: comparison of measured κxy/T with electronic estimate from Wiedemann-Franz law; extraction of characteristic temperature T₀ from fit of λxy = λ0 * tanh(T₀/T); comparison with calculated phonon and magnon dispersions
  • 观察: characteristic energyT₀ = 48 K → 4.1 meV; magnon-phonon crossing span = 3.2 meV (and 1.4 meV); close correspondence of energy scales
• interpretation — Magnon–phonon hybridization due to spin-density-wave order is the primary mechanism for the enhanced phonon thermal Hall effect, and this coupling may soften optical phonons under pressure to suppress antiferromagnetism and promote superconductivity.
  • 方法: physical argument that SDW order introduces magnon bands hybridizing with phonons, imparting Berry curvature
  • 观察: observed SDW and magnon bands in La₄Ni₃O₁₀ from prior studies