In-Plane Anisotropy in the Layered Topological Insulator Ta₂Ni₃Te₅ Investigated via TEM and Polarized Raman Spectroscopy

Ta₂M₃Te₅, (M = Pd, Ni) has emerged as a platform to study 2D topological insulators, which have unusual properties such as gapless surface states and spin-momentum locking. In particular, Ta₂Ni₃Te₅ has been shown to host superconductivity under pressure and is predicted to host second-order topology. In this work, we use TEM and polarized Raman spectroscopy (PRS) to study the anisotropic properties of exfoliated few-layer Ta₂Ni₃Te₅. Electron diffraction and TEM imaging were used to probe the structural anisotropic response of the material. Angle-resolved PRS was used to investigate the vibrational modes of the material, including their angular dependence, symmetries, and excitation energy dependence.