  We report the results of polarization-dependent Raman spectroscopy of phonon
states in single-crystalline quasi-one-dimensional NbTe$_4$ and TaTe$_4$ van
der Waals materials. The measurements were conducted in the wide temperature
range from 80 K to 560 K. Our results show that although both materials have
identical crystal structures and symmetries, there is a drastic difference in
the intensity of their Raman spectra. While TaTe4 exhibits well-defined peaks
through the examined frequency and temperature ranges, NbTe4 reveals extremely
weak Raman signatures. The measured spectral positions of the phonon peaks
agree with the phonon band structure calculated using the density-functional
theory. We offer possible reasons for the in-tensity differences between the
two van der Waals materials. Our results provide insights into the phonon
properties of NbTe$_4$ and TaTe$_4$ van der Waals materials and indicate the
potential of Raman spectroscopy for studying charge-density-wave quantum
condensate phases.
