We report the results of polarization-dependent Raman spectroscopy of phonon states in single-crystalline quasi-one-dimensional NbTe₄ and TaTe₄ van der Waals materials. The measurements were conducted in the wide temperature range from 80 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 wavenumber 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 intensity differences between the two van der Waals materials. Our results provide insights into the phonon properties of NbTe₄ and TaTe₄ van der Waals materials and indicate the potential of Raman spectroscopy for studying charge-density-wave quantum condensate phases.

中文翻译：

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NbTe4 和 TaTe4 准一维范德华晶体中声子态的拉曼光谱

我们报告了单晶准一维 NbTe ₄和 TaTe ₄范德华材料中声子态的偏振相关拉曼光谱结果。测量是在 80 至 560 K 的宽温度范围内进行的。我们的结果表明，尽管两种材料具有相同的晶体结构和对称性，但它们的拉曼光谱强度存在巨大差异。虽然 TaTe ₄在检查的波数和温度范围内表现出明确的峰，但 NbTe ₄显示出极弱的拉曼特征。测量的声子峰的光谱位置与使用密度泛函理论计算的声子能带结构一致。我们提供了两种范德华材料之间强度差异的可能原因。我们的结果深入了解了 NbTe ₄和 TaTe ₄范德华材料的声子特性，并表明拉曼光谱在研究电荷密度波量子凝聚相方面的潜力。