Thickness and Spin Dependence of Raman Modes in Magnetic Layered Fe₃GeTe₂

Abstract

2D layered Fe3GeTe2 has attracted increasing attention due to its high magnetic ordering temperature and novel physical properties. Lattice dynamics is a fundamental property of Fe3GeTe2, and its relationships with the number of layers and interlayer spin ordering have not yet been explored in depth. Here, by first‐principles density functional theory calculations, the phonon vibrations and Raman intensities of Fe3GeTe2 are systematically studied from the bulk to monolayer structures. Furthermore, the spin‐phonon coupling effect is investigated by considering different interlayer magnetic orderings: ferromagnetic and antiferromagnetic. It is found that the frequencies of Raman modes in Fe3GeTe2 exhibit considerable dependence on the layer number and spin ordering. The results not only reveal the notable spin‐phonon interactions in Fe3GeTe2, but also demonstrate that Raman modes can be utilized for characterizing the sample thickness and interlayer spin ordering in this 2D magnet.

Mesoscale interplay between phonons and crystal electric field excitations in quantum spin liquid candidate CsYbSe2

“…The intensity of a Raman mode is I p |e s ÁR ˜Áe T i | 2 , where R ˜is the Raman tensor of a phonon mode, and e s and e i are the electric polarization vectors of the scattered and incident light, respectively. 60,61 In the back-scattering geometry with linear laser polarization, e s and e i are in plane. Based on the Raman tensors shown in the ESI, ‡ it is clear that only A 1g and E 2g phonon modes can appear in the Raman spectra, whereas E 1g modes cannot be observed in our experimental configuration.…”

Raman Spectra of Bulk and Few-Layer GeSe From First-Principles Calculations

“…However, few shifts are induced between bilayer and trilayer. Our calculation suggests that GeSe has a large Raman shift with increasing layer thickness compared to other 2D materials (Lee et al, 2010;Tan et al, 2012;Yagmurcukardes et al, 2018;Kong et al, 2021). It provides a valuable approach for distinguishing the structure between monolayer and few-layer GeSe.…”

Nearly-Resonant Crystalline-Phononic Coupling in Quantum Spin Liquid Candidate CsYbSe$_2$

“…Based on the Raman tensors shown in the Supplemental Information, it is clear that only A 1g and E 2g phonon modes can appear in the Raman spectra, whereas E 1g modes cannot be observed in the our experimental configuration. This is common in hexagonal layered materials56 . Our DFT calculated frequencies for the two E 2g modes (E 1 2g and E 2 2g ) are 37 cm −1 and 97 cm −1 , and A 1g at 122 cm −1 .…”

“…, where R is the Raman tensor of a phonon mode, and e s and e i are the electric polarization vectors of the scattered and incident light, respectively 55,56 . In the back-scattering geometry with linear laser polarization, e s and e i are in plane.…”

“…The bulk unit cell has a hexagonal lattice with 8 atoms in total, giving rise to 24 normal phonon modes at the Γ point: Γ(D 6h ) = A 1g + 3A 2u + 2B 1u + 2B 2g + E 1g + 2E 2g + 3E 1u + 2E 2u , where Raman active phonon modes correspond to non-degenerate A 1g symmetry modes, doubly degenerate E 2g symmetry modes, and doubly degenerate E 1g symmetry modes. The intensity of a Raman mode isI ∝ |e s • R • e T i | 2, where R is the Raman tensor of a phonon mode, and e s and e i are the electric polarization vectors of the scattered and incident light, respectively55,56 . In the back-scattering geometry with linear laser polarization, e s and e i are in plane.…”