Dataset for "Identification of Soft Modes Across the Commensurate-to-Incommensurate Charge Density Wave Transition in 1T-TaSe2"

The dataset contains the inputs necessary to reproduce the theoretical calculations presented in the associated paper, the abstract of which is as follows:

1T-TaSe2 is a prototypical charge density wave (CDW) material for which electron-phonon coupling and associated lattice reconstruction play an important role in driving and stabilising the CDW phase. Here, we investigate the lattice dynamics of bulk 1T-TaSe2 using angle-resolved ultralow wavenumber Raman spectroscopy down to 10 cm−1. Our high-resolution Raman spectra allow us to identify at least 27 peaks in the commensurate (CCDW) phase in the region 50 - 300 cm−1. Contrary to other layered materials, we do not find evidence of interlayer breathing or shear modes, suggestive of AA stacking in the bulk. Polarisation dependence of the mode intensities allows the assignment of their symmetry, which is supported by calculations of the phonon frequencies for the bulk structure using density functional theory. A detailed temperature dependence in the range T = 80 - 500 K allows us to clearly identify the soft modes associated with the CDW superlattice. Above the commensurate (CCDW) to incommensurate (ICCDW) phase transition at 473 K, we observe a dramatic loss of resolution of all modes, and significant linewidth broadening associated with a reduced phonon lifetime as the charge-order becomes incommensurate with the lattice.