Tuning spinaron and Kondo resonances via quantum confinement

Controlling zero-bias anomalies in magnetic atoms provides a promising strategy to engineer tunable quantum many-body excitations. Here we show how two different quantum impurities featuring spinaron and Kondo excitations can be controlled via quantum confinement engineering by using circular quantum corrals on a Ag(111) surface. In corrals built from both Ag and Co adatoms, the width of the zero-bias anomaly in the central Co adatom oscillates as a function of corral radius with a period of half of the Ag(111) surface state wavelength. Parameters extracted for Co/Ag(111) show only small differences in the extracted spinaron zero-bias anomaly between corral walls built from Ag or Co adatoms. In quantum corrals occupied by metal-free phthalocyanine, a S=1/2 Kondo system, we observe notable changes in the zero-bias anomaly line shape as a function of corral radius. Our results offer insight into many-body Kondo and spinaron resonances in which the electronic density is controlled by confinement engineering.