标题： CeGaGe候选Weyl半金属的结构表征 显示英文标题

标题： Structural characterization of the candidate Weyl semimetal CeGaGe

摘要： 外尔半金属具有多种有趣的物理性质，包括与导电态共存的拓扑保护电子态。在导电材料中利用拓扑保护态对于技术应用前景广阔。在外尔半金属形成于非中心对称结构且含有磁矩的情况下，可能会出现许多在磁性、中心对称外尔材料中无法观察到的新现象。当化合物中的两种原子具有几乎相同的原子序数时，在某些情况下，使用标准的粉末X射线衍射仪很难明确区分中心对称结构与其非中心对称子群，就像候选外尔半金属CeGaGe的情况一样。在这种情况下，高角度单晶中子衍射实验可以为X射线衍射提供互补信息，并明确解决中心对称和非中心对称晶体结构之间的任何歧义。对候选外尔半金属CeGaGe的单晶中子衍射测量确认其结构是非中心对称的，属于空间群109 $\left(I4_1md\right)$而不是中心对称的空间群141 $\left(I4_1/amd\right)$。数据集中有许多高角度反射，这些反射提供了清晰且直观的物理证据，表明CeGaGe以 $I4_1md$对称形式存在，因为这些反射的Bragg平面可以包含Ga而不含Ge，或者反之亦然，而具有 $I4_1/amd$对称性的结构的Bragg平面会有Ga和Ge的混合。此外，在我们研究的一些晶体中，有明确的证据表明从体心 $I4_1md$对称性向原始 $P4_3$和/或 $P4_1$对称性的结构转变。 显示英文摘要

摘要： Weyl semimetals have a variety of intriguing physical properties, including topologically protected electronic states that coexist with conducting states. Possible exploitation of topologically protected states in a conducting material is promising for technological applications. Weyl semimetals that form in a noncentrosymmetric structure that also contain magnetic moments may host a variety of emergent phenomena that cannot be seen in magnetic, centrosymmetric Weyl materials. It can be difficult to distinguish definitively between a centrosymmetric structure and one of its noncentrosymmetric subgroups with standard powder X-ray diffractometers in cases where two atoms in the compound have nearly the same atomic number, as is the case for the candidate Weyl semimetal CeGaGe. In these cases, a careful single-crystal neutron diffraction experiment with high-angle reflections provides complimentary information to X-ray diffraction and definitively resolves any ambiguity between centrosymmetric and noncentrosymmetric crystal structures. Single-crystal neutron diffraction measurements on the candidate Weyl semimetal CeGaGe confirm that its structure is noncentrosymmetric, described by space group 109 $\left(I4_1md\right)$ rather than the centrosymmetric space group 141 $\left(I4_1/amd\right)$. There are many high-angle reflections in the data set that give clear, physically intuitive evidence that CeGaGe forms with $I4_1md$ symmetry since Bragg planes of these reflections can contain Ga with no Ge or vice versa, whereas the Bragg planes for a structure with $I4_1/amd$ symmetry would have a mix of Ga and Ge. Further, in some crystals we have studied, there is clear evidence for a structural transition from body-centered $I4_1md$ symmetry to primitive $P4_3$ and/or $P4_1$ symmetry.