'Kondo state' and Kondo resonance in a two-dimensional electron gas

TL;DR

This study investigates the Kondo state and resonance in a two-dimensional electron gas using atomic-scale microscopy, revealing the first observation of the Kondo state linked to ferromagnetic RKKY interactions in a 2DEG system.

Contribution

It reports the first direct detection of the Kondo state in a 2DEG system influenced by ferromagnetic RKKY interactions at the atomic scale.

Findings

Detection of the unobserved Kondo state in a 2DEG system.

Visualization of the screening electron cloud in real space.

Evidence of RKKY-mediated ferromagnetic interactions affecting Kondo phenomena.

Abstract

The delicate balance of spin-screening and spin-aligning interactions determines many of the peculiar properties of dilute magnetic systems. We study a surface-supported all-organic multi-impurity Kondo spin system at the atomic scale by low-temperature scanning tunnelling microscopy and -spectroscopy. The model system consists of spin-1/2 radicals that are aligned in one-dimensional chains and interact via a ferromagnetic RKKY interaction mediated by the 2DEG of the supporting substrate. Due to the RKKY-induced enhanced depopulation of one spin-subband in the 2DEG, we finally succeeded to detect the so far unobserved 'Kondo state' as opposed to the well-established Kondo resonance. Its cloud of screening electrons, that are virtually bound to the radicals below the Kondo temperature, represents the extended exchange hole of the ferromagnetically polarized spin chain imaged here in real space.