在单质固体中发现混合拓扑量子态
Discovery of a hybrid topological quantum state in an elemental solid
AI总结：
本文在单质固体砷中通过隧道显微术、光电子能谱和理论分析发现并验证了一种由强拓扑与高阶拓扑联合形成的混合拓扑相，为探索不同能带拓扑相互作用及拓扑导电通道应用提供了新平台。
摘要：
拓扑与相互作用是现代量子物质理解中的基础概念。二者的结合产生了三个重要研究方向：不同相互作用之间的竞争，如多重交织相；相互作用与拓扑之间的相互影响，驱动了扭转层状材料和拓扑磁体中的现象；以及多种拓扑序的融合，从而产生独特的新相。前两个方向已发展为重要研究领域，而最后一个方向在很大程度上仍未被探索，主要原因是缺乏可用于实验研究的材料平台。在此，我们利用隧道显微术、光电子能谱和理论分析，在简单的单质固体砷中揭示了一种“混合”且新颖的拓扑物质相。通过独特的体-表面-边缘对应关系，我们发现砷具有强拓扑与高阶拓扑的联合特征，从而稳定了一种混合拓扑相。动量空间能谱测量显示出拓扑表面态的迹象，而实空间显微测量则揭示了在表面各种天然纳米结构上由拓扑诱导的台阶边缘导电通道的独特几何形态。利用理论模型，我们证明砷中无带隙台阶边缘态的存在依赖于非平庸强Z2不变量与非平庸高阶拓扑不变量的同时出现，从而为混合拓扑及其在单晶中的实现提供了实验证据。我们的发现凸显了探索不同种类能带拓扑之间相互作用以及在未来工程量子或纳米器件中利用相关拓扑导电通道的途径。
英文摘要：
Topology and interactions are foundational concepts in the modern understanding of quantum matter. Their nexus yields three significant research directions: competition between distinct interactions, as in the multiple intertwined phases, interplay between interactions and topology that drives the phenomena in twisted layered materials and topological magnets, and the coalescence of multiple topological orders to generate distinct novel phases. The first two examples have grown into major areas of research, while the last example remains mostly untouched, mainly because of the lack of a material platform for experimental studies. Here, using tunneling microscopy, photoemission spectroscopy, and theoretical analysis, we unveil a "hybrid" and yet novel topological phase of matter in the simple elemental solid arsenic. Through a unique bulk-surface-edge correspondence, we uncover that arsenic features a conjoined strong and higher-order topology, stabilizing a hybrid topological phase. While momentum-space spectroscopy measurements show signs of topological surface states, real-space microscopy measurements unravel a unique geometry of topology-induced step edge conduction channels revealed on various forms of natural nanostructures on the surface. Using theoretical models, we show that the existence of gapless step edge states in arsenic relies on the simultaneous presence of both a nontrivial strong Z2 invariant and a nontrivial higher-order topological invariant, providing experimental evidence for hybrid topology and its realization in a single crystal. Our discovery highlights pathways to explore the interplay of different kinds of band topology and harness the associated topological conduction channels in future engineered quantum or nano-devices.
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