Emergence of Quasi-One-Dimensional van Hove Singularity in Kagome Metal RbV3Sb5.

The divergence of the density of states (DOS) near the Fermi energy plays a critical role in strengthening electron correlations. van Hove singularities (vHS) are a common source of this DOS divergence, and their characteristics depend on the dimensionality of electron dispersion. The atomic arrangement on the surface can alter the effective dimensionality of electron dispersion and, consequently, vHS. In V-based Kagome metals AV3Sb5 (A = K, Rb, and Cs), the saddle-shaped dispersion results in two-dimensional vHS. Intriguingly, the surface arrangement of atoms in a Kagome lattice can reduce the effective dimensionality of electron dispersion, enhancing electron correlations. By taking advantage of nearly closed shell electronic character of Rb atoms, their linear arrangement imposes a one-dimensional localized potential on the underlying Kagome lattice. As a result, we observe a significantly increased divergence of DOS along with an augmentation of the charge density wave, potentially driven by reinforced electronic correlations.