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Lattice Dynamics, Phonon Chirality, and Spin–Phonon Coupling in 2D Itinerant Ferromagnet Fe<inf>3</inf>GeTe<inf>2</inf>

Du, L and Tang, J and Zhao, Y and Li, X and Yang, R and Hu, X and Bai, X and Wang, X and Watanabe, K and Taniguchi, T and Shi, D and Yu, G and Bai, X and Hasan, T and Zhang, G and Sun, Z (2019) Lattice Dynamics, Phonon Chirality, and Spin–Phonon Coupling in 2D Itinerant Ferromagnet Fe<inf>3</inf>GeTe<inf>2</inf>. Advanced Functional Materials, 29. ISSN 1616-301X

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Abstract

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 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 A1g(Γ) and one E2g(Γ) phonons. The doubly degenerate E2g(Γ) 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.

Item Type: Article
Subjects: UNSPECIFIED
Divisions: UNSPECIFIED
Depositing User: Cron Job
Date Deposited: 27 Nov 2019 20:01
Last Modified: 25 Jun 2020 10:29
DOI: 10.1002/adfm.201904734