A Fermi Arc Ladder Reveals Higher-Fold Topology*

While topological insulators and Weyl semimetals have been major topics within materials research, theoretical and experimental focus has begun to shift to more exotic forms of topological quantum matter. Higher-fold topology is one example, where the low-energy description goes beyond Standard Model analogs. Despite intensive experimental studies, conclusive evidence remains elusive for the topological nature of higher-fold chiral fermions. In this work, we leverage a photoemission spectroscopy probe to discover the multi-gap topology of a higher-fold chiral fermion material [1]. We identify two sets of chiral surface states. These Fermi arcs exhibit an emergent ladder structure in energy-momentum space, unprecedented in topological materials. Furthermore, we determine the multi-gap chiral charge C=(2,2). Our results provide a general framework to explore future complex topological materials.

[1] Preprint at arXiv:2004.11365.