Kondo temperature when the Fermi level is near a step in the conduction density of states

TL;DR

This paper investigates how the Kondo temperature varies when the Fermi level approaches a step in the conduction density of states, revealing power-law relationships influenced by hybridization ratios and energy parameters.

Contribution

It provides a theoretical analysis of the Kondo temperature near a conduction band edge, incorporating surface and bulk hybridizations and their effects on low-temperature impurity behavior.

Findings

Kondo temperature follows power laws near the band edge

Dependence of T_K on hybridization ratios and energy parameters

Analytical expressions for T_K as a function of D_s and ε_F

Abstract

The (111) surface of Cu, Ag and Au is characterized by a band of surface Shockley states, with constant density of states beginning slightly below the Fermi energy. These states as well as bulk states hybridize with magnetic impurities which can be placed above the surface. We calculate the characteristic low-temperature energy scale, the Kondo temperature $T_K$ of the impurity Anderson model, as the bottom of the conduction band $D_s$ crosses the Fermi energy $\epsilon_F$. We find simple power laws $T_K \simeq |D_s-\epsilon_F|^{\eta}$, where $\eta$ depends on the sign of $D_s-\epsilon_F$, the ratio between surface and bulk hybridizations with the impurity $\Delta_s/\Delta_b$ and the ratio between on-site and Coulomb energy $E_d/U$ in the model.