Fe₃GeTe₂与Fe₅GeTe₂中各向异性电子-声子-自旋耦合的对比：一项 helicity 分辨拉曼研究
Contrasting anisotropic electron-phonon-spin coupling in Fe$_{3}$GeTe$_{2}$ and Fe$_{5}$GeTe$_{2}$: A helicity-resolved Raman study
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- Indian Institute of Technology Kharagpur（印度理工学院卡拉格普尔分校）
- Jawaharlal Nehru University（贾瓦哈拉尔·尼赫鲁大学）
- Institute of Nuclear Physics, Polish Academy of Sciences（波兰科学院核物理研究所）
- Sungkyunkwan University（成均馆大学）
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中文总结 AI 辅助
本研究通过 helicity 分辨拉曼光谱对比 Fe₃GeTe₂与Fe₅GeTe₂的各向异性电子-声子-自旋耦合，揭示二者耦合特性差异及晶体结构、磁各向异性的调控作用。
中文摘要 AI 辅助
二维范德华铁磁体 Fe₃GeTe₂（F3GT）与 Fe₅GeTe₂（F5GT）表现出显著的磁光响应，为研究晶格、电子与磁自由度间的相互作用提供了极具前景的平台。本文利用波长依赖及温度依赖的 helicity 分辨拉曼光谱，对这些体系中光共振诱导的各向异性电子-声子耦合及其与磁有序的关联展开对比研究。通过在左、右圆偏振激发下分辨双重简并的 E 模，研究发现手性模分裂（Δf）的温度演化并不追踪磁化强度行为，表明 helicity 依赖的拉曼响应不仅源于磁有序导致的时间反演对称性破缺，还与自旋轨道耦合的电子相互作用相关。值得注意的是，F3GT 中面外磁化强度在光共振下间接调控面内各向异性电子-声子耦合，而 F5GT 表现出静态各向异性相互作用。Fano 不对称参数 1/q 揭示了声子与电子连续体间的模依赖及温度依赖耦合强度，F3GT 存在显著的角各向异性，而 F5GT 呈各向同性——这源于其多个 Fe 位点及更强的层间杂化。研究结果阐明了晶体结构与磁各向异性在塑造这些层状金属铁磁体中各向异性耦合电子-声子-自旋动力学的作用，并突出 FeₓGeTe₂ 作为多功能平台，可用于深入探究层状金属铁磁体中的手性光-物质相互作用。
英文摘要
Two-dimensional van der Waals ferromagnets Fe$_3$GeTe$ _2$ (F3GT) and Fe$_5$GeTe$_2$ (F5GT) exhibit pronounced magneto-optical responses, which open promising platforms for investigating the interplay among lattice, electronic, and magnetic degrees of freedom. Here, we present a comparative study of optical resonance-induced anisotropic electron-phonon coupling and its association with magnetic ordering in these systems using wavelength- and temperature-dependent helicity-resolved Raman spectroscopy. By resolving the doubly degenerate E modes under left- and right-circularly polarized excitations, we demonstrate that the temperature evolution of the chiral mode splitting ($Δf$) does not track the magnetization behavior, indicating that the helicity-dependent Raman response arises not solely from time-reversal symmetry breaking due to magnetic order, but also from spin-orbit-coupled electronic interactions. Notably, in F3GT, the out-of-plane magnetization indirectly governs the in-plane anisotropic electron-phonon coupling under optical resonance, whereas F5GT exhibits static anisotropic interactions. The Fano asymmetry parameter $1/q$ reveals mode- and temperature-dependent coupling strengths between phonons and the electronic continuum, with pronounced angular anisotropy in F3GT but isotropic behavior in F5GT--- a consequence of its multiple Fe sites and enhanced interlayer hybridization in the latter. Our results demonstrate the role of crystal structure and magnetic anisotropy in shaping the anisotropically coupled electron-phonon-spin dynamics in these layered metallic ferromagnets, and highlight Fe$_n$GeTe$_2$ as a versatile platform for microscopic insight into chiral light-matter interactions in layered metallic ferromagnets.
