The quantum behaviour of electrons in materials is the foundation of modern electronics and information technology1–11, and quantum materials with topological electronic and optical properties are essential for realizing quantized electronic responses that can be used for next generation technology. Here we report the first observation of topological quantum properties of chiral crystals6,7 in the RhSi family. We find that this material class hosts a quantum phase of matter that exhibits nearly ideal topological surface properties originating from the crystals’ structural chirality. Electrons on the surface of these crystals show a highly unusual helicoid fermionic structure that spirals around two high-symmetry momenta, indicating electronic topological chirality. The existence of bulk multiply degenerate band fermions is guaranteed by the crystal symmetries; however, to determine the topological invariant or charge in these chiral crystals, it is essential to identify and study the helicoid topology of the arc states. The helicoid arcs that we observe on the surface characterize the topological charges of ±2, which arise from bulk higher-spin chiral fermions. These topological conductors exhibit giant Fermi arcs of maximum length (π), which are orders of magnitude larger than those found in known chiral Weyl fermion semimetals5,8–11. Our results demonstrate an electronic topological state of matter on structurally chiral crystals featuring helicoid-arc quantum states. Such exotic multifold chiral fermion semimetal states could be used to detect a quantized photogalvanic optical response, the chiral magnetic effect and other optoelectronic phenomena predicted for this class of materials6.Angle-resolved photoemission spectroscopy measurements reveal that CoSi and RhSi are nearly ideal topological conductors, with structural chirality and surface helicoid arcs of topological charge ±2 arising from bulk multifold chiral states.

中文翻译：

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具有螺旋-弧量子态的拓扑手性晶体

材料中电子的量子行为是现代电子和信息技术的基础1-11，具有拓扑电子和光学特性的量子材料对于实现可用于下一代技术的量子化电子响应至关重要。在这里，我们报告了对 RhSi 家族中手性晶体 6,7 拓扑量子特性的首次观察。我们发现该材料类别具有物质的量子相，该相具有源自晶体结构手性的近乎理想的拓扑表面特性。这些晶体表面的电子显示出极不寻常的螺旋状费米子结构，该结构围绕两个高对称动量盘旋，表明电子拓扑手性。晶体对称性保证了体多简并带费米子的存在；然而，要确定这些手性晶体中的拓扑不变量或电荷，必须识别和研究弧态的螺旋拓扑。我们在表面观察到的螺旋弧表征了 ±2 的拓扑电荷，这些拓扑电荷来自大量的高自旋手性费米子。这些拓扑导体表现出最大长度 (π) 的巨大费米弧，比已知的手性外尔费米子半金属 5,8-11 中发现的要大几个数量级。我们的结果证明了具有螺旋-弧量子态的结构手性晶体上物质的电子拓扑状态。这种奇特的多重手性费米子半金属态可用于检测量化的光电流光学响应，