Topological surface states and flat bands in the kagome superconductor CsV₃Sb₅

Exotic quantum phenomena may appear in material systems with multiple orders or phases, where the mutual interactions can give rise to new physics beyond that of each component. Here, we report spectroscopic evidence for a unique combination of topology and correlation effects in the kagome superconductor CsV₃Sb₅. Topologically nontrivial surface states are observed near the Fermi energy (E_F), indicating that the topological physics may be active upon entering the superconducting state. Flat bands are observed, suggesting that electron correlation effects are also at play in this system. Our results reveal the peculiar electronic structure of CsV₃Sb₅, which holds the potential for realizing Majorana zero modes and anomalous superconducting states in kagome lattices. They also establish CsV₃Sb₅ as a unique platform for exploring the interactions between the charge order, topology, correlation effects and superconductivity.