Kondo physics of magnetic adatoms on metallic surfaces when the onset of the surface conduction density of states crosses the Fermi level

Abstract

We study the role of the onset of Shockley states, Ds, belonging to (111) surfaces of Cu, Ag and Au in the Kondo effect when a magnetic impurity is deposited on them. When Ds approaches to the Fermi level, EF , thing that can be done by compressing (stretching) the metallic sample, we found that most of the thermodynamic and dynamic properties of the impurity are affected in a non trivial way. We model the system by a generic Anderson impurity model and solve it by using the numerical renormalization group, NRG, technique. In particular, the impurity contribution to magnetic susceptibility and entropy as a function of temperature exhibit negative values and goes to zero slowly in a logarithmic shape. Furthermore, we found a suppression of the spectral density weight at the Fermi level when Ds ∼ EF even in the Kondo regime. As a consequence, the conductance through the impurity is strongly reduced by near 25% of the unitary value 2e 2 /h. Finally, we analyze these features in realistic systems like Co on Ag(111) reported in the literature.

Universal scaling of tunable Yu-Shiba-Rusinov states across the quantum phase transition

“…Therefore, this reasoning can be ruled out as outlined in Supplementary Note 3. However, a realistic structured electronic band and non-constant density of states can modify the Kondo physics in a non-trivial way [58][59][60] and thus go beyond the simple assumption of the universal scaling. It is therefore intriguing to investigate the validity or breakdown of the universal scaling in weakly coupled systems like certain molecules and in systems with non-trivial band structure.…”

Numerical renormalization group study of the Loschmidt echo in Kondo systems

“…For this purpose, we employ the time-dependent numerical renormalization group (tNRG) approach 19 – 21 , implemented in the matrix product state formalism 22 , 35 . More specifically, the one-channel Kondo model (1CK) effectively describes a single spin one-half impurity in bulk material or connected to external electronic reservoir, dynamical mean-field lattice models mapped on impurity model 18 , adatoms on surfaces 36 , 37 , qubit in environment 38 , 39 , etc. On the other hand, multi-channel (two-channel in our case, 2CK) Kondo model describes single impurity connected to multiple independent bands 34 , 40 , 41 or could be effectively used to describe multiple impurity systems 42 – 48 .…”