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PreprintarXiv licencearXiv

Contrasting anisotropic electron-phonon-spin coupling in Fe3GeTe2 and Fe5GeTe2: A helicity-resolved Raman study

  • Smrutiranjan Mekap
  • Jyoti Saini
  • Andrzej Ptok
  • Pawan Kumar Srivastava
  • Changgu Lee
  • Subhasis Ghosh
  • Anushree Roy
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Abstract

Two-dimensional van der Waals ferromagnets Fe3GeTe$ _2$ (F3GT) and Fe5GeTe2 (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 FenGeTe2 as a versatile platform for microscopic insight into chiral light-matter interactions in layered metallic ferromagnets.

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Cite

BibTeXRIS
BibTeX
@misc{mekap2026contrasting,
  title = {{Contrasting anisotropic electron-phonon-spin coupling in Fe$_3$GeTe$_2$ and Fe$_5$GeTe$_2$: A helicity-resolved Raman study}},
  author = {Smrutiranjan Mekap and Jyoti Saini and Andrzej Ptok and Pawan Kumar Srivastava and Changgu Lee and Subhasis Ghosh and Anushree Roy},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2608.03193},
  eprint = {2608.03193},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.03193},
}
RIS
TY  - UNPB
TI  - Contrasting anisotropic electron-phonon-spin coupling in Fe_3GeTe_2 and Fe_5GeTe_2: A helicity-resolved Raman study
AU  - Smrutiranjan Mekap
AU  - Jyoti Saini
AU  - Andrzej Ptok
AU  - Pawan Kumar Srivastava
AU  - Changgu Lee
AU  - Subhasis Ghosh
AU  - Anushree Roy
PY  - 2026
DA  - 2026/10/05
PB  - arXiv
DO  - 10.48550/arxiv.2608.03193
UR  - https://arxiv.org/abs/2608.03193
AB  - Two-dimensional van der Waals ferromagnets Fe_3GeTe$ _2$ (F3GT) and Fe_5GeTe_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_nGeTe_2 as a versatile platform for microscopic insight into chiral light-matter interactions in layered metallic ferromagnets.
ER  -