Evolution of Electronic Structure in Pristine and Rb-Reconstructed Surfaces of Kagome Metal RbV₃Sb₅

We report on in situ low-temperature (4 K) scanning tunneling microscope measurements of atomic and electronic structures of the cleaved surfaces of an alkali-based kagome metal RbV₃Sb₅ single crystals. We find that the dominant pristine surface exhibits Rb-1×1 structure, in which a unique unidirectional √3a₀ charge order is discovered. As the sample temperature slightly rises, Rb-√3×1 and Rb-√3×√3 reconstructions form due to desorption of surface Rb atoms. Our conductance mapping results demonstrate that Rb desorption not only gives rise to hole doping but also reconstructs the electronic band structures. Surprisingly, we find a ubiquitous gap opening near the Fermi level in tunneling spectra on all the surfaces despite their large differences of hole-carrier concentration, indicating an orbital-selective band reconstruction in RbV₃Sb₅. The Rb desorption induced electronic reconstructions are further confirmed by our density functional theory calculations.