Competition between quantum spin tunneling and Kondo effect

TL;DR

This paper investigates the competition and crossover between quantum spin tunneling and Kondo effect in quantized spins, using a generalized Anderson model to predict spectral features observable via scanning tunneling spectroscopy.

Contribution

It models the crossover between QST and Kondo effects in a generalized Anderson model including magnetic anisotropy, revealing new spectral features such as split-Kondo peaks.

Findings

Integer spins can exhibit split-Kondo peaks driven by QST.

Spectral features distinguish QST from Kondo effects.

Proposes experimental probes for the crossover using spectroscopy.

Abstract

Quantum spin tunneling (QST) and Kondo effect are two very different quantum phenomena that produce the same effect on quantized spins, namely, the quenching of their magnetization. However, the nature of this quenching is very different so that QST and Kondo effects compete with each other. Importantly, both QST and Kondo produce very characteristic features in the spectral function that can be measured by means of single spin scanning tunneling spectroscopy that makes it possible to probe the crossover from one regime to the other. We model this crossover, and the resulting changes in transport, using a non-perturbative treatment of a generalized Anderson model including magnetic anisotropy that leads to quantum spin tunneling. We predict that, at zero magnetic field, integer spins can feature a split-Kondo peak driven by quantum spin tunneling.