Protected Metallic Edge States in a Graphene-Capped Quantum Spin Hall System

Epitaxial bismuthene on SiC(0001) hosts symmetry-protected metallic edge states within a large bulk band gap, establishing it as a promising two-dimensional topological insulator for high-temperature quantum spin Hall (QSH) transport. Here we realize bismuthene islands by intercalating Bi beneath zero-layer graphene on SiC(0001) followed by hydrogen treatment, yielding well-defined edge terminations. Spectroscopic measurements demonstrate the metallic edge states originating from the underlying bismuthene layer. The graphene overlayer interacts only weakly with the bismuthene, preserving its topological character while providing environmental protection. Overall, our results establish graphene-capped bismuthene as a robust and tunable platform for studying correlated quantum states, with the one-dimensional edge channels exhibiting signatures of electronic correlation effects.