Spin-charge separation and simultaneous spin and charge Kondo effect

TL;DR

This paper investigates the simultaneous occurrence of spin and charge Kondo effects in a model with an impurity possessing both spin and isospin, revealing their independence in the continuum limit and their persistence under lattice effects.

Contribution

It demonstrates that spin and charge Kondo effects can occur simultaneously at any coupling strength, and explores their behavior across different models and conditions.

Findings

Spin and charge Kondo effects can occur simultaneously.

Universal spin and charge Kondo effects persist despite lattice effects.

Similar behavior observed in two-impurity Anderson models.

Abstract

We study the spin-charge separation in a Kondo-like model for an impurity with a spin and a charge (isospin) degree of freedom coupled to a single conduction channel (the ``spin-charge'' Kondo model). We show that the spin and charge Kondo effects can occur simultaneously at any coupling strength. In the continuum (wide-band or weak coupling) limit, the Kondo screening in each sector is independent, while at finite bandwidth and strong coupling the lattice effects lead to a renormalization of the effective Kondo exchange constants; nevertheless, universal spin and charge Kondo effects still occur. We find similar behavior in the two-impurity Anderson model with positive and negative electron-electron interaction and in the two-impurity Anderson-Holstein model with a single phonon mode. We comment on the applicability of such models to describe the conductance of deformable molecules with a local magnetic moment.