# Fully compensated Kondo effect for a two-channel spin S=1 impurity

## TL;DR

This paper investigates the low-temperature behavior of a two-channel Anderson impurity model with an S=1 impurity, revealing unique Kondo effects, the influence of magnetic anisotropy, and differences from the standard S=1/2 model, relevant for Ni impurities in Au chains.

## Contribution

It introduces a detailed analysis of an S=1 impurity in a two-channel Anderson model, highlighting novel Kondo phenomena and the impact of magnetic anisotropy, extending understanding beyond the conventional S=1/2 case.

## Key findings

- Distinct Kondo temperature and spectral features for S=1 impurity
- Magnetic anisotropy D induces non-Landau Fermi liquid behavior
- Negative D suppresses the Kondo effect significantly

## Abstract

We study the low-temperature properties of the generalized Anderson impurity model in which two localized configurations, one with two doublets and the other with a triplet, are mixed by two degenerate conduction channels. By using the numerical renormalization group and the non-crossing approximation, we analyze the impurity entropy, its spectral density, and the equilibrium conductance for several values of the model parameters. Marked differences with respect to the conventional one-channel spin $s=1/2$ Anderson model, that can be traced as hallmarks of an impurity spin $S=1$, are found in the Kondo temperature, the width and position of the charge transfer peak, as well as the temperature dependence of the equilibrium conductance. Furthermore, we analyze the rich effects of a single-ion magnetic anisotropy $D$ on the Kondo behavior. In particular, as shown before, for large enough positive $D$ the system behaves as a "non-Landau" Fermi liquid that cannot be adiabatically connected to a non-interacting system turning off the interactions. For negative $D$ the Kondo effect is strongly suppressed. The model studied is suitable for a comprehensive analysis for recent investigations of a single Ni impurity embedded into an Au chain.