Lattice Dynamics, Phonon Chirality, and Spin–Phonon Coupling in 2D Itinerant Ferromagnet Fe3GeTe2

Luojun Du, Jian Tang, Yanchong Zhao, Xiaomei Li, Rong Yang, Xuerong Hu, Xueyin Bai, Xiao Wang, Kenji Watanabe, Takashi Taniguchi, Dongxia Shi, Guoqiang Yu, Xuedong Bai, Tawfique Hasan, Guangyu Zhang, Zhipei Sun

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article number1904734
Number of pages8
JournalAdvanced Functional Materials
Volume29
Issue number48
Early online date25 Sep 2019
DOIs
Publication statusPublished - 28 Nov 2019
MoE publication typeA1 Journal article-refereed

Keywords

  • chirality of phonons
  • Fe3GeTe2
  • itinerant ferromagnet
  • Raman susceptibility
  • spin-phonon coupling
  • RAMAN-SCATTERING

Projects

PREIN: Photonics Research and Innovation

Mäkelä, K.

01/01/201931/12/2022

Project: Academy of Finland: Other research funding

LAYERED 2D MATERIALS BASED THZ SPECTROSCOPY AND IMAGING

Hulkko, E., Sun, Z., Das, S., Generalov, A. & Uddin, M.

01/01/201831/12/2021

Project: Academy of Finland: Other research funding

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