标题： 厚度依赖的菱形多层石墨烯中的拓扑相和平带 显示英文标题

标题： Thickness-dependent Topological Phases and Flat Bands in Rhombohedral Multilayer Graphene

摘要： 菱方多层石墨烯已成为研究奇异量子态（如超导性和分数反常量子霍尔效应）的一个非凡平台，这主要是由于存在拓扑表面平带。 尽管进行了大量研究，但对其从薄层到体材料的电子结构演变的系统光谱研究仍然缺乏。 使用先进的角分辨光电子能谱技术，具有亚微米空间分辨率，我们直接探测并追踪菱方多层石墨烯的拓扑电子结构的厚度演变。 随着层数的增加，有隙子带转变为在动量空间中螺旋的三维狄拉克节点；而平带始终在费米能级附近被观察到，并最终演化为拓扑鼓头表面态。 这种独特的厚度依赖性拓扑相变可以通过薄层中的1D Su-Schrieffer-Heeger链的三维推广，到体极限中的拓扑狄拉克节点螺旋半金属来很好地捕捉。 我们的发现为在菱方多层石墨烯中探索具有非平凡拓扑和关联效应的奇异量子相奠定了坚实的基础。 显示英文摘要

摘要： Rhombohedral multilayer graphene has emerged as an extraordinary platform for investigating exotic quantum states, such as superconductivity and fractional quantum anomalous Hall effects, mainly due to the existence of topological surface flatbands. Despite extensive research efforts, a systematic spectroscopic investigation on the evolution of its electronic structure from thin layers to bulk remains elusive. Using state-of-the-art angle-resolved photoemission spectroscopy with submicron spatial resolution, we directly probe and trace the thickness evolution of the topological electronic structures of rhombohedral multilayer graphene. As the layer number increases, the gapped subbands transform into the 3D Dirac nodes that spirals in the momentum space; while the flatbands are constantly observed around Fermi level, and eventually evolve into the topological drumhead surface states. This unique thickness-dependent topological phase transition can be well captured by the 3D generalization of 1D Su-Schrieffer-Heeger chain in thin layers, to the topological Dirac nodal spiral semimetal in the bulk limit. Our findings establish a solid foundation for exploring the exotic quantum phases with nontrivial topology and correlation effects in rhombohedral multilayer graphene.