Anisotropic electron-phonon coupling and chiral phonons in van der Waals room temperature ferromagnet Fe$_{5}$GeTe$_{2}$ (2512.19910v1)

Abstract: The layered van der Waals Fe$_5$GeTe$_2$ (F5GT) compound exhibits room-temperature ferromagnetism, making it a promising candidate for technological applications. In our study, combined temperature- and polarization-dependent Raman measurements, along with modern {\it ab initio} calculations, reveal important aspects of the lattice dynamics. The angle dependence of Raman intensity under linear polarization configuration exhibits a strong tilt in the laboratory coordinate, indicating the existence of anisotropic electron-phonon coupling. The electron-phonon coupling was also examined via the Fano parameter of the asymmetric peak in the Raman spectra. Finally, the threefold rotational symmetry guarantees the existence of chiral phonons. We present direct spectroscopic evidence for these chiral vibrational modes through cross-circularly polarized Raman measurements, complemented by theoretical calculations of phonon circular polarization. Together, these results identify F5GT as an ideal platform for investigating emergent couplings among lattice, electronic, and magnetic degrees of freedom and for advancing the understanding of chiral phonons in magnetic van der Waals materials.