Sr₂IrO₄中局域相互作用与基态选择的拉曼磁振子光谱研究
Raman magnon spectroscopy of local interactions and ground state selection in $\mathrm{Sr_2IrO_4}$
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中文总结 AI 辅助
该研究通过角分辨拉曼偏振测量，结合高压实验与线性自旋波计算，揭示了Sr₂IrO₄中压力诱导的磁异质性源于弱层间相互作用变化，证实拉曼活性磁振子可放大基态选择的μeV级相互作用。
中文摘要 AI 辅助
量子材料中相互竞争且耦合的自旋与电荷相互作用会产生多种有序态，其中局域构型优先影响长程有序。当这些相互作用在能量上精细平衡时，无序与涨落会发挥显著作用。拉曼散射因对局域环境敏感且能揭示整体对称性，特别适合揭示此类情形下的基础物理。我们对关联层状磁体Sr₂IrO₄的单晶开展角分辨拉曼偏振测量，该材料的莫特绝缘基态源于强自旋轨道耦合。我们通过在ab面及垂直面几何下从10至700 cm⁻¹的全面测量，表征声子与磁振子模的对称性，并在带穿孔金刚石的金刚石对顶砧中追踪这些模在12 GPa压力下的演化。压力未显著改变晶格，因为声子模在压缩下线性位移，但与此同时磁振子模变得与位置相关且分布在一定波数范围内。我们将这种磁异质性归因于压力增强的弱层间相互作用变化，这可能在局域上倾向于相互竞争的磁堆叠构型，并将实验结果与线性自旋波计算的预测进行比较。我们的结果表明，拉曼活性磁振子将负责基态选择的μeV级相互作用放大为易于测量的光谱变化。
英文摘要
Competing and coupled spin and charge interactions in quantum materials lead to a variety of ordered states where local configurations preferentially influence the long-range order. When these interactions are finely balanced in energy, disorder and fluctuations play an outsized role. Raman scattering is particularly well-suited to revealing the underlying physics in such situations because of its sensitivity to local environments and ability to reveal overall symmetries. We perform angle-resolved Raman polarization measurements on single crystals of the correlated, layered magnet, \ce{Sr2IrO4}, where the Mott insulating ground state arises from strong spin-orbit coupling. We characterize the symmetries of both the phonon and magnon modes through comprehensive measurements in both the $ab$-plane and out-of-plane geometries from 10 to 700 cm$^{-1}$, and trace the evolution of these modes in both configurations to 12 GPa in a diamond anvil cell with perforated diamonds. Pressure does not significantly alter the lattice as the phonon modes shift linearly under compression, but at the same time the magnon modes become position dependent and spread over a range of wavenumbers. We attribute this magnetic heterogeneity to pressure-enhanced variations in the weak interlayer interactions, which may locally favor competing magnetic stacking configurations, and compare our experimental results to the predictions of linear spin wave calculations. Our results demonstrate that Raman-active magnons amplify $μ$eV-scale interactions responsible for ground-state selection into easily measurable spectral changes.
