Surface Reconstruction Induced Co Kondo Resonance Width Modulation On One Monolayer Ag Covered Cu(111)

The Kondo effect has been capturing the interest of both experimentalists and theorists since its discovery in early 1930s.The effect arises from the scattering of nonmagnetic-host conduction electrons by the local spin of a magnetic impurity.As the temperature of the system blow the Kondo temperature,a singlet state is formed enhancing the local density of states(LDOS)near the Fermi energy(the Kondo resonance)at the site of the impurity.Therefore,the Kondo effect can be probed by the low-temperature scanning tunneling microscopy(LT-STM).The control of the spin-electron interaction in a nondestructive and reversible manner may have strong potentials in applications such as spintronics and quantum information processing.Thus,the modulation of Kondo temperature Tk,which is proportional to the Kondo resonance width has attracted many efforts.A recent work by Li et al.demonstrated that the surface states confined by quantum corral can significantly tune the Kondo temperature of Co single adatom on Ag(111).The surface states on reconstructed 1ML-Ag/Cu(111)surface can also be modulated by superstructure.So we expect that the superstructure may offer another route to modulate the Kondo effect.However,previous study only showed a single value of the Kondo resonance width for Co single adatom deposited on reconstructed 1ML-Ag/Cu(111)surface.In this article,we performed a systematic study of the Kondo effect of single Co adatom on 1ML-Ag/Cu(111)surface.Utilizing atomic manipulation,we placed the Co single adatom to the different positions of the reconstructed 1ML-Ag/Cu(111)surface and performed the spectroscopy measurements for the Co adatom at low temperature.We find that the Kondo resonance width of the Co adatom shows apparent variation with the position.The obtained Kondo resonance width at hcp/fcc boundary is generally wider than the one measured at fcc area.The measured Kondo resonance width at fcc area is found to have a strong correlation with the probed position-dependent LDOS.In addition,we performed the tight binding(TB)calculations to calculate local density of states(LDOS)of surface states.By comparing the experimental data and TB calculated one,we attributed the surface-state electrons is main reason to the modulated LDOS.With a recently reported model which includes the contribution of both the bulk and surface states to the Kondo effect,we extracted the exchange values of bulk-adatom(Jb)and surface-adatom(Js)for Co on 1ML-Ag/Cu(111),respectively.These findings clarify the role of surface reconstruction on the Kondo effect.