Untangling charge-order dependent bulk states from surface effects in a topological kagome metal ScV6Sn6

Kagome metals with charge density wave (CDW) order exhibit a broad spectrum of intriguing quantum phenomena. The recent discovery of the novel kagome CDW compound ScV6Sn6 has spurred significant interest. However, understanding the interplay between CDW and the bulk electronic structure has been obscured by a profusion of surface states and terminations in this quantum material. Here, we employ photoemission spectroscopy and potassium dosing to elucidate the complete bulk band structure of ScV6Sn6, revealing multiple van Hove singularities near the Fermi level. We surprisingly discover a robust spin -polarized topological Dirac surface resonance state at the M point within the twofold van Hove singularities. Assisted by first -principles calculations, the temperature dependence of the kz-resolved angle -resolved photoemission spectroscopy spectrum root root provides unequivocal evidence for the proposed 3x 3x3 charge order over other candidates. Our work not only enhances the understanding of the CDW-dependent bulk and surface states in ScV6Sn6, but also establishes an essential foundation for potential manipulation of the CDW order in kagome materials.