The quasi-one-dimensional chiral compound ${\left({\mathrm{TaSe}}_4\right)}_2\mathrm{I}$ has been extensively studied as a prime example of a topological Weyl semimetal. Upon crossing its phase transition temperature $T_{\mathrm{CDW}}\approx 263\mathrm{K}, {\left({\mathrm{TaSe}}_4\right)}_2\mathrm{I}$ exhibits incommensurate charge density wave (CDW) modulations described by the well-defined propagation vector $\sim (0.05,0.05,0.11)$, oblique to the ${\mathrm{TaSe}}_4$ chains. Although optical and transport properties greatly depend on chirality, there is no systematic report about chiral domain size for ${\left({\mathrm{TaSe}}_4\right)}_2\mathrm{I}$. In this study, our single-crystal scattering refinements reveal a bulk iodine deficiency, and Flack parameter measurements on multiple crystals demonstrate that separate ${\left({\mathrm{TaSe}}_4\right)}_2\mathrm{I}$ crystals have uniform handedness, supported by direct imaging and helicity-dependent terahertz emission spectroscopy. Our single-crystal x-ray scattering and calculated diffraction patterns identify multiple diffuse features and create a real-space picture of the temperature-dependent ${\left({\mathrm{TaSe}}_4\right)}_2\mathrm{I}$ crystal structure. The short-range diffuse features are present at room temperature and decrease in intensity as the CDW modulation develops. These transverse displacements, along with electron pinning from the iodine deficiency, help explain why ${\left({\mathrm{TaSe}}_4\right)}_2\mathrm{I}$ behaves as an electronic semiconductor at temperatures above and below $T_{\mathrm{CDW}}$, despite a metallic band structure calculated from density functional theory of the ideal structure.

中文翻译：

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单手性 (TaSe4)2I 晶体中的无序和漫散射

准一维手性化合物${（{\mathrm{硒化钽}}_4）}_2\mathrm{我}$作为拓扑外尔半金属的主要例子已被广泛研究。当超过其相变温度时${\mathrm{时间}}_{\mathrm{CDW}}\approx 263\mathrm{K}, {（{\mathrm{硒化钽}}_4）}_2\mathrm{我}$表现出由明确定义的传播矢量描述的不相称的电荷密度波 (CDW) 调制$～（0.05,0.05,0.11）$，倾斜于${\mathrm{硒化钽}}_4$链。尽管光学和传输特性很大程度上取决于手性，但目前还没有关于手性域大小的系统报告${（{\mathrm{硒化钽}}_4）}_2\mathrm{我}$。在这项研究中，我们的单晶散射改进揭示了整体碘缺乏，并且对多个晶体的 Flack 参数测量表明，单独的碘缺乏${（{\mathrm{硒化钽}}_4）}_2\mathrm{我}$晶体具有均匀的旋向性，由直接成像和螺旋度相关的太赫兹发射光谱支持。我们的单晶 X 射线散射和计算的衍射图案可识别多个漫射特征，并创建温度相关的真实空间图像${（{\mathrm{硒化钽}}_4）}_2\mathrm{我}$晶体结构。短程漫射特征在室温下存在，并且随着 CDW 调制的发展而强度降低。这些横向位移以及缺碘引起的电子钉扎有助于解释原因${（{\mathrm{硒化钽}}_4）}_2\mathrm{我}$在高于和低于温度下表现得像电子半导体${\mathrm{时间}}_{\mathrm{CDW}}$，尽管金属能带结构是根据理想结构的密度泛函理论计算出来的。