*

A layered, transition-metal dichalcogenide (TMD), TaSe₂ continues to attract interest for advanced device applications. In bulk form, metallic TaSe₂ exhibits transitions between commensurate and incommensurate charge-density wave (CDW) phases. In the present work, we extend our opto-thermal Raman measurements¹ on MoS₂ to include bulk TaSe₂ in both 1T and 2H crystallographic phases. A novel, magneto-Raman microscope system affords measurement of low-frequency (down to 10 cm^-1) vibrational modes as a function of both temperature (100 to 400)K and magnetic field (0 to 9)T. The dependence of the observed Raman-active phonons on temperature and magnetic field will be presented and compared with earlier results on MoS₂. Specifically, we observe the appearance of low-frequency, zone-folded modes in the CDW state, which soften with temperature similar to the higher frequency, in-plane E_2g mode. Additionally, we compare the measured magneto-Raman results to calculations using ab initio, density functional theory.

¹ R. Yan, J. R. Simpson, et al., ACS Nano 8, 986 (2014).