The tetrachalcogenide TaTe₄ is known as an excellent example of a charge-density wave (CDW) system that has a commensurately modulated structure at room temperature. Using density function perturbation theory, we find that the unmodulated phase of TaTe₄ has a giant Kohn anomaly at room temperature, which manifests itself as softened phonon modes at the CDW vector $(1/2a^{*},1/2b^{*},1/3c^{*})$. Interestingly, after the application of 8 GPa hydrostatic pressure, this CDW instability can be effectively suppressed and disappears at room temperature. By studying the topology of the Fermi surface and the phonon linewidth, we show that the Kohn anomaly in TaTe₄ is driven by a large electron–phonon coupling coefficient at the CDW vector and not by Fermi surface nesting.

中文翻译：

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TaTe4中Kohn异常的第一性原理研究

四硫属化物 TaTe ₄被称为电荷密度波 (CDW) 系统的一个很好的例子，该系统在室温下具有相应的调制结构。使用密度函数微扰理论，我们发现 TaTe ₄的未调制相在室温下具有巨大的 Kohn 异常，这表现为 CDW 矢量处的软化声子模式$(1/2{\mathrm{一种}}^{*},1/2{乙}^{*},1/3C^{*})$. 有趣的是，在施加 8 GPa 静水压力后，这种 CDW 不稳定性可以被有效抑制并在室温下消失。通过研究费米表面的拓扑结构和声子线宽，我们表明 TaTe ₄中的 Kohn 异常是由 CDW 矢量处的大电子 - 声子耦合系数驱动的，而不是由费米表面嵌套驱动的。