Layer Architecture Shapes Electronic, Magnetic, and Lattice Interactions in Ruddlesden-Popper Nickelates

摘要

利用Ni L₃边和O K边共振非弹性X射线散射（RIXS）对La₃Ni₂O₇的两种多形体——交替单层-三层结构LNO-1313与双层结构LNO-2222——以及三层化合物La₄Ni₃O₁₀进行了系统比较。研究发现，LNO-1313与La₄Ni₃O₁₀的电子、磁性和晶格激发高度相似，而双层LNO-2222表现出明显不同的特征。与LNO-2222相比，LNO-1313和La₄Ni₃O₁₀具有更弱的轨道极化、增强的3d8L（配体空穴）特性、较小的面外磁交换尺度以及更强的电子-声子耦合。在有效局域矩框架下，强反铁磁层间耦合产生的自旋激发可由纠缠二聚体图像自然描述，其优势在层间耦合超过层内相互作用的双层LNO-2222中最明显。这些结果为层状镍酸盐中与超导相关的低能物理理论模型提供了关键实验约束。

材料

• La₃Ni₂O₇ alternating monolayer-trilayer (LNO-1313)
• La₃Ni₂O₇ bilayer (LNO-2222)
• La₄Ni₃O₁₀

方法

• resonant inelastic x-ray scattering (RIXS)
• Ni L₃-edge RIXS
• O K-edge RIXS
• x-ray diffraction (XRD)
• high-pressure floating-zone crystal growth
• damped harmonic oscillator (DHO) fitting
• Heisenberg Hamiltonian modeling
• entangled-unit generalized spin-wave calculations

关键词

• superconductivity
• magnetic excitations
• electron phonon coupling
• orbital polarization
• charge transfer excitations
• spin charge stripe order
• interlayer antiferromagnetic coupling
• entangled dimer scenario
• ligand hole character

亮点

• First comprehensive RIXS characterization of LNO-1313 spanning electronic, magnetic, and lattice excitations.
• First momentum-resolved RIXS evidence that magnetic correlations in LNO-1313 more closely resemble those of trilayer La₄Ni₃O₁₀ than those of bilayer LNO-2222.
• O K-edge RIXS identifies bond-buckling and bond-stretching phonon modes in nickelates for the first time.
• Unusually pronounced bond-stretching phonon overtones up to eight times the phonon energy in La₄Ni₃O₁₀ indicate very strong electron-phonon coupling.
• The entangled-dimer formalism captures both magnetic-excitation dispersion and spectral-weight momentum dependence, outperforming conventional spin-wave theory especially in LNO-2222.

结论

• RIXS measurements provide a comparative view of electronic, magnetic, and lattice excitations in bilayer LNO-2222, alternating monolayer-trilayer LNO-1313, and trilayer La₄Ni₃O₁₀.
• The bilayer compound exhibits excitation spectra that differ from those of the other two materials, whereas the layer-alternating and trilayer compounds show unexpectedly similar responses across all three excitation channels.
• Compared with LNO-2222, LNO-1313 and La₄Ni₃O₁₀ have weaker orbital polarization, enhanced 3d8L character, a reduced out-of-plane magnetic-exchange scale, and stronger electron-phonon coupling.
• The magnetic excitations in LNO-2222 are better described as triplons than as conventional magnons within an entangled-dimer and spin-charge stripe framework.
• Layer architecture plays a central role in shaping the coupled electronic, magnetic, and lattice degrees of freedom of Ruddlesden-Popper nickelates.

主要论断

本批次暂无数据。

研究流程

本批次暂无数据。