Emergent 3×3 charge order on the Cs reconstruction of kagome superconductor CsV 3 Sb 5

The alkali adatoms with controlled coverage on the surface have been demonstrated to effectively tune the surface band of quantum materials through in situ electron doping. However, the interplay of orderly arranged alkali adatoms with the surface states of quantum materials remains unexplored. Here, by using low-temperature scanning tunneling microscopy/spectroscopy (STM/S), we observed the emergent 3×3 super modulation of electronic states on the 3 × 3 R 30 ° (R3) Cs ordered surface of kagome superconductor CsV 3 Sb 5 . The nondispersive 3×3 superlattice at R3 ordered surface shows contrast inversion in positive and negative differential conductance maps, indicating a charge order origin. The 3×3 charge order is suppressed with increasing temperature and undetectable at a critical temperature of ∼62 K. Furthermore, in the Ta substituted sample CsV 2.6 Ta 0.4 Sb 5 , where long-range 2×2×2 charge density wave is significantly suppressed, the 3×3 charge order on the R3 ordered surface becomes blurred and much weaker than that in the undoped sample. It indicates that the 3×3 charge order on the R3 ordered surface is directly correlated to the bulk charge density waves in CsV 3 Sb 5 . Our work provides a new platform for understanding and manipulating the cascade of charge orders in kagome superconductors.