Lattice Dynamics, Phonon Chirality, and Spin-Phonon Coupling in 2D Itinerant Ferromagnet Fe3GeTe2
Lattice Dynamics, Phonon Chirality, and Spin-Phonon Coupling in 2D Itinerant Ferromagnet Fe3GeTe2
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DOI：
10.1002/adfm.201904734
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发表时间：
2019-09-25
影响因子：
19
通讯作者：
Sun, Zhipei
中科院分区：
文献类型：
--
作者：
Du, Luojun;Tang, Jian;Sun, Zhipei
Fe_3GeTe_2由于其二维巡游铁磁性、拓扑节线和近藤晶格行为而成为最引人注目的货车范德华晶体之一。然而，这种材料中的晶格动力学、声子的手性和自旋-声子耦合，这些为这些奇异现象奠定了基础，仍然没有被探索。在这里，第一个实验研究的声子和自旋和晶格自由度之间的相互作用在几层Fe 3GeTe 2的报道。结果表明，室温下存在三个显著的拉曼模：两个A（1g）（Gamma）声子和一个E-2g（Gamma）声子。双简并E-2g（Gamma）模反转了入射光子的螺旋度，表明了赝角动量和手征。通过对Fe_3GeTe_2中声子能量和寿命随温度变化的分析，确定了Fe_3GeTe_2中的自旋-声子耦合。晶格振荡和自旋之间的这种相互作用显著增强了拉曼敏感性，允许在低温温度范围内观察到两个额外的拉曼模式。此外，在环境条件下的激光辐射诱导的Fe 3GeTe 2和相应的拉曼指纹的退化被揭示。结果提供了第一个实验分析的声子在这种新型的二维巡游铁磁体和进一步的基础研究和应用开发的适用性。
Fe3GeTe2 has emerged as one of the most fascinating van der Waals crystals due to its 2D itinerant ferromagnetism, topological nodal lines, and Kondo lattice behavior. However, lattice dynamics, chirality of phonons, and spin-phonon coupling in this material, which set the foundation for these exotic phenomena, have remained unexplored. Here, the first experimental investigation of the phonons and mutual interactions between spin and lattice degrees of freedom in few-layer Fe3GeTe2 is reported. The results elucidate three prominent Raman modes at room temperature: two A(1g)(Gamma) and one E-2g(Gamma) phonons. The doubly degenerate E-2g(Gamma) mode reverses the helicity of incident photons, indicating the pseudoangular momentum and chirality. Through analysis of temperature-dependent phonon energies and lifetimes, which strongly diverge from the anharmonic model below Curie temperature, the spin-phonon coupling in Fe3GeTe2 is determined. Such interaction between lattice oscillations and spin significantly enhances the Raman susceptibility, allowing to observe two additional Raman modes at the cryogenic temperature range. In addition, laser radiation-induced degradation of Fe3GeTe2 in ambient conditions and the corresponding Raman fingerprint is revealed. The results provide the first experimental analysis of phonons in this novel 2D itinerant ferromagnet and their applicability for further fundamental studies and application development.