Doping from CDW to topological superconductivity: The role of defects on phonon scattering in the non-centrosymmetric PbxTaSe2

The vibrational and electronic properties of the Pb-doped dichalcogenide PbxTaSe2 (x = 0, 0.25, 0.33, 0.5, 0.75, and 1) have been investigated using Raman scattering experiments. A marked variation of the main vibrational modes with Pb concentration x is observed. The concentration dependence of the vibrational modes resembles the dependence of the vibrational modes in TaSe2 on the number of crystallographic layers along the c-axis direction. The temperature and polarization dependences of Raman spectra of PbxTaSe2 revealed additional broad modes in the low-frequency regime, which are discussed in the context of the remnant charge density wave, induced disorder, or PbSe phase formed in the interface of Pb and TaSe2 layers.