Scanning tunneling spectroscopic evidence of crossover transition in the two-impurity Kondo problem

TL;DR

This paper uses numerical renormalization group calculations to analyze scanning tunneling spectroscopy data, revealing a crossover transition in the two-impurity Kondo problem characterized by a shift from peak to dip structures near the Fermi level.

Contribution

It provides the first detailed theoretical analysis of the crossover transition in the two-impurity Kondo problem using NRG and STS data.

Findings

Peak structure in dI/dV spectra diminishes with decreasing coupling.

Dip structure appears near Fermi level indicating strong antiferromagnetic correlation.

Transition from peak to dip structure signifies a crossover in the Kondo problem.

Abstract

We calculate the differential conductance (dI/dV) corresponding to scanning tunneling spectroscopy (STS) measurements for two magnetic atoms adsorbed on a metal surface with the aid of the numerical renormalization group (NRG) technique. We find that the peak structure of the dI/dV spectra near the Fermi level changes gradually as a function of the adatom separation and the coupling between the adatoms and the metal surface conduction band. When the coupling becomes small, the peak disappears and, instead, a dip structure appears near the Fermi level. This dip structure is the manifestation of the strong antiferromagnetic correlation between the localized spins. The gradual change of the dI/dV structure from a peak structure to a dip structure originates from the crossover transition in the two impurity Kondo problem.