Hysteresis of the nearly-commensurate to commensurate charge density wave phase transition in tantalum disulfide using Raman spectroscopy

The structure of tantalum disulfide at various temperatures was investigated through vibrational mode analysis using Raman scattering. Incident and scattered light was analyzed through polarization in order to decompose broadened features, allowing for the characterization of individual mode behavior. Temperature dependence of the vibrational modes in the region surrounding the nearly-commensurate to commensurate charge density wave phase transition shows strong hysteretic behavior. The widely-referenced macroscopic resistivity measurements, used in determining the charge density wave phase transition, have a different hysteresis. The resistivity displays sharp discontinuities at the phase transition whereas local vibrational mode measurements display a continuous evolution. The hysteresis of the vibrational modes extends over a significantly larger range than that of the resistivity. I conclude that tantalum disulfide has inhomogeneous, local structure on the microscopic scale.