论文标题
拓扑Weyl半毛Tap的偏光性拉曼光谱中的异常声子模式依赖性
Anomalous Phonon-mode Dependence in Polarized Raman Spectroscopy of Topological Weyl Semimetal TaP
论文作者
论文摘要
拓扑Weyl半法（WSM）由于手性的Weyl fermions和表面费米弧而引起了广泛的兴趣，从而实现了独特的光学和运输现象。在这项工作中，我们提出了TAP的角度分辨的拉曼光谱，这是一种典型的非中心对称WSM，用于五个激发波长，范围为364至785 nm。拉曼活动模式，$ a_1 $，$ b_1^1 $和$ b_1^2 $模式，展示了传统拉曼理论之外的两个主要独特功能。首先，拉曼活动模式的相对强度随激发波长的函数而变化。其次，角度分辨的极化拉曼光谱显示出与拉曼张量理论的系统偏差。特别是，对于633 nm的激发，$ b_1^1 $模式不存在，而$ b_1^2 $模式显示出不寻常的两倍对称性，而不是488、532和633 nm激励的四倍对称性。这些非常规现象归因于由于存在多个具有几乎相同能量但对称性不同的多个载流子袋，因此在拉曼过程中的干扰效应。
Topological Weyl semimetals (WSMs) have attracted widespread interests due to the chiral Weyl fermions and surface Fermi arcs that enable unique optical and transport phenomena. In this work, we present angle-resolved Raman spectroscopy of TaP, a prototypical noncentrosymmetric WSM, for five excitation wavelengths ranging from 364 to 785 nm. The Raman active modes, $A_1$, $B_1^1$, and $B_1^2$ modes, exhibit two main unique features beyond the conventional Raman theory. First, the relative intensities of Raman active modes change as a function of the excitation wavelength. Second, angle-resolved polarized Raman spectra show systematic deviation from the Raman tensor theory. In particular, the $B_1^1$ mode is absent for 633 nm excitation, whereas the $B_1^2$ mode shows an unusual two-fold symmetry instead of a four-fold symmetry for 488, 532, and 633 nm excitations. These unconventional phenomena are attributed to the interference effect in the Raman process owing to the existence of multiple carrier pockets with almost the same energy but different symmetries.
