Surface region band enhancement in noble-gas adsorption assisted angle-resolved photoemission spectroscopy on the kagome superconductor ${\mathrm{RbV}}_3{\mathrm{Sb}}_5$

Electronic states near surface regions can be distinct from bulk states, which are paramount in understanding various physical phenomena occurring at surfaces and in applications in semiconductors, energy, and catalysis. Here, we report an abnormal surface region band enhancement effect in angle-resolved photoemission spectroscopy on kagome superconductor ${\mathrm{RbV}}_3{\mathrm{Sb}}_5$, by depositing noble gases with fine control. In contrast to conventional surface contamination, the intensity of the surface region Sb band can be enhanced more than three times with noble-gas adsorption. In the meantime, a hole-doping effect is observed for the enhanced surface region band, with other bands hardly changing. The doping effect is more pronounced with heavier noble gases. We propose that noble-gas atoms selectively fill alkali metal vacancy sites on the surface, which improves the surface condition, boosts surface region bands, and effectively dopes it with the Pauli repulsion mechanism. Our results provide a unique and reversible way to improve surface conditions and tune surface region bands by controlled surface noble-gas deposition.