Revisiting a Classic Kondo-System: Co/Cu(111)

Single cobalt atoms on the (111) surfaces of noble metals were long time considered prototypical systems of the Kondo effect in STM experiments [1]. Spectroscopic measurements on these atoms reveal a Fano-like dip around the Fermi-level, which was explained by two interfering tunneling paths of electrons, one directly into the surface and the second one into a Kondo resonance. However, Bouaziz et al. [2] recently proposed that the observed feature actually originates from spin-flip excitations of the Co atom spin induced by the tunneling electrons. Further, interaction between these spin-flip excitations and conduction electrons was predicted to lead to the formation of a new quasiparticle, called spinaron.

We performed scanning tunneling spectroscopy measurements on Co atoms on a Cu(111) surface in magnetic fields of up to 12 T providing new insight into the underlying physics of this system. These new experimental results and possible explanations will be discussed.

[1] Science 280, 567 (1998); Nature 403, 512 (2000); PRB 65, 121406 (2002)

[2] Nat. Commun. 11, 6112 (2020)