Probing electron-phonon and phonon-phonon coupling in type-II Dirac semi-metal NiTe₂ via temperature-dependent Raman spectroscopy

We report the temperature-dependent structural characterization of type-II Dirac semimetal NiTe2 in the form of a bulk single crystal and a nanoflake (200 nm thick). Detailed x-ray diffraction study along with Rietveld refinement analysis reveals superior crystallinity and linear thermal expansion coefficient (alpha ( T )) of 5.56 x 10(-6) and 22.5 x 10(-6) K-1 along a or b and c lattice directions, respectively. Temperature evolution of Raman spectra shows non-linear variations in the phonon frequency and full-width half maxima of the out-of-plane A 1g g modes. Raman mode E 2g1