Layer breathing Raman mode in two-dimensional van der Waals magnet Cr2Ge2Te6

Abstract

We report the observation of a weak broad mode with characteristic dependence on thickness of flakes suggesting this as a layer breathing (LB) mode in Cr2Ge2Te6 (CGT) measured using Raman spectroscopy. Symmetry analysis confirms that the CGT falls under the non-polar category of layered material. The evolution of the LB mode frequency with increasing layer number ( N) reveals a distinct softening trend, characteristic of weakening restoring forces in thicker flakes. By fitting the experimental Raman data using the linear chain model (LCM), we quantitatively extract the interlayer force constant ( Kc), providing a measure of the vdW coupling strength between layers. The good agreement between experimental and theoretical results establishes the LCM as a reliable framework for describing interlayer phonon dynamics in CGT. In conclusion, these findings not only deepen our understanding of interlayer interactions and symmetry-driven phonon behavior but also offer a powerful diagnostic for assuming layer thickness and structural integrity in vdW magnets. Such insights are pivotal for 2D spintronics and multifunctional device architectures based on CGT.