Transition metal dichalcogenides (TMDs) are a set of inorganic crystals that can be isolated into atomically-thin, 2D layers. TMDs can be semiconducting, insulating, metallic, and superconducting. Tantalum diselenide (TaSe2) is a metallic TMD that undergoes a Peierls transition to an incommensurate charge density wave phase below 123 K and a commensurate charge density wave below 90 K. Raman spectroscopy is a sensitive probe to these subtle changes in the lattice structure. In particular, transitioning to charge density wave states leads to new low frequency Raman peaks. In our work, we investigate the temperature dependence of the Raman modes of bulk and 2D TaSe2. We monitor the intensity, Raman shift, and FWHM of the normal Raman modes as a function of temperature. Additionally, we observe the emergence of new low frequency Raman modes indicative of the charge density wave states. We compare the critical temperature of the transitions to the incommensurate and commensurate charge density wave states for thin (&lt;10 nm) and bulk samples. Finally, we discuss the conclusions that can be drawn about the origins of the charge density wave state in TaSe2 from the thickness dependence of the critical temperatures and theory calculations.

Using Raman spectroscopy to observe the charge density wave states in metallic tantalum diselenide

254th National Meeting (2017)

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