Twofold van Hove singularity and origin of charge order in topological kagome superconductor CsV₃Sb₅

The layered vanadium antimonides AV₃Sb₅ (A = K, Rb, Cs) are a recently discovered family of topological kagome metals that exhibit a range of strongly correlated electronic phases including charge order and superconductivity. However, it is not yet understood how the singularities inherent to the kagome electronic structure are linked to the observed many-body phases. Here, we combine angle-resolved photoemission spectroscopy and density functional theory to reveal multiple kagome-derived van Hove singularities (vHS) coexisting near the Fermi level of CsV₃Sb₅ and analyze their contribution to electronic symmetry breaking. The vHS in CsV₃Sb₅ are characterized by two distinct sublattice flavors – pure (p)-type and mixed (m)-type – which critically determines the pairing symmetry and ground states emerging in AV₃Sb₅ series. We establish that, among the multiple vHS in CsV₃Sb₅, the m-type vHS of the d_xz/d_yz kagome band and the p-type vHS of the d_xy/d_x2-y2 kagome band cross the Fermi level to allow electronic symmetry breaking. The former band exhibits pronounced Fermi surface nesting, while the latter contributes via higher-order vHS. Our work reveals the essential role of kagome-derived vHS for the collective phenomena realized in the AV₃Sb₅ family.