论文标题
观察Kagome Metal CSV $ _3 $ SB $ _5 $中异常振幅模式
Observation of anomalous amplitude modes in the kagome metal CsV$_3$Sb$_5$
论文作者
论文摘要
电荷密度波（CDW）相通常伴随着软声声子模式的冷凝，从而导致晶格失真和电荷密度调制。根据缺乏软声子的证据，最近发现的Kagome Metal CSV $ _3 $ SB $ _5 $挑战了这张照片。在这里，我们报告了这种材料中拉曼活性CDW振幅模式的观察，这些模式通常是集体激发，通常被认为是从冷冻的软声子中出现的。振幅模式与其他超级晶格模式强烈杂交，以清晰的温度依赖频移和扩展为赋予它们，在其他已知的CDW材料中很少见。模式混合和较大的振幅模式频率都表明，CDW表现出强电子 - 音波耦合的特征，在这种方案中，声音声子软化可以不复存在。在没有软声音的情况下，观察幅度模式突出了CSV $ _3 $ SB $ _5 $中CDW的非常规性。
The charge-density wave (CDW) phase is often accompanied by the condensation of a soft acoustic phonon mode, giving rise to lattice distortion and charge density modulation. This picture was challenged for the recently discovered kagome metal CsV$_3$Sb$_5$, based on the evidence of absence of soft phonons. Here we report the observation of Raman-active CDW amplitude modes in this material, which are collective excitations typically thought to emerge out of frozen soft phonons. The amplitude modes strongly hybridize with other superlattice modes, imparting them with clear temperature-dependent frequency shift and broadening, rarely seen in other known CDW materials. Both the mode mixing and the large amplitude mode frequencies suggest that the CDW exhibits the character of strong electron-phonon coupling, a regime in which acoustic phonon softening can cease to exist. The observation of amplitude modes in the absence of soft phonons highlights the unconventional nature of the CDW in CsV$_3$Sb$_5$.
