Spectral evolution of the SU(4) Kondo effect from the single impurity to the two-dimensional lattice

TL;DR

This paper explores how the SU(4) Kondo effect evolves from a single magnetic impurity to a 2D lattice, using a Hubbard-Anderson model to analyze differential conductance in various impurity arrangements, aligning with recent experimental findings.

Contribution

It introduces a Hubbard-Anderson model for a 2D array with orbital degeneracy and demonstrates its relevance to experimental observations of the SU(4) Kondo effect.

Findings

Orbital degeneracy is crucial for the SU(4) Kondo effect.

Results match experimental data on iron(II) phthalocyanine molecules on Au(111).

First experimental realization of a 2D SU(4) Kondo lattice system.

Abstract

We describe the evolution of the SU(4) Kondo effect as the number of magnetic centers increases from one impurity to the two-dimensional (2D) lattice. We derive a Hubbard-Anderson model which describes a 2D array of atoms or molecules with two-fold orbital degeneracy, acting as magnetic impurities and interacting with a metallic host. We calculate the differential conductance, observed typically in experiments of scanning tunneling spectroscopy, for different arrangements of impurities on a metallic surface: a single impurity, a periodic square lattice, and several sites of a rectangular cluster. Our results point towards the crucial importance of the orbital degeneracy and agree well with recent experiments in different systems of iron(II) phtalocyanine molecules deposited on top of Au(111) [N. Tsukahara et al., Phys. Rev. Lett. 106, 187201 (2011)], indicating that this would be the first experimental realization of an artificial 2D SU(4) Kondo-lattice system.