Inelastic X-ray spectroscopic investigation of the 2D CDW compound 1T-TaS2

1T-TaS2, a strongly correlated material exhibiting a series of charge-density-wave (CDW) transitions at different temperatures (see Figure 1(a)), has intrigued researchers for more than 40 years [1-3]. More recently, spin liquid and heavy fermion behavior have been reported at the monolayer limit [4], triggered by the multiple-q CDWs, but the experimental momentum-resolved phonon structure, its lattice dynamics, and the putative soft mode are still missing. This calls for a detailed study to understand the phononic contribution to CDW formation, in particular the phonon softening of specific acoustic phonon branches. We intend to comprehensively measure the temperature and momentum dependence of the low-energy acoustic and optical phonons utilizing high-resolution inelastic x-ray scattering (IXS).