Hubbard chain with a Kondo impurity

TL;DR

This paper provides an exact Bethe Ansatz solution for a Hubbard chain with a Kondo impurity, confirming the existence of strong-coupling fixed points and analyzing magnetic properties across different fillings.

Contribution

It introduces a Bethe Ansatz solution for the Hubbard chain with a Kondo impurity and explores the fixed points and magnetic properties in this model.

Findings

Existence of strong-coupling fixed points with ferromagnetic Kondo coupling.

Ground state spin depends on impurity spin S, being S-1/2.

Wilson ratio varies with density and interaction away from half-filling.

Abstract

A Bethe Ansatz solution of a (modified) Hubbard chain with a Kondo impurity of arbitrary spin S at a highly symmetric line of parameter space is proposed and explored. Our results confirm the existence of a strong-coupling (line of) fixed-point(s) with ferromagnetic Kondo coupling as first hypothetized by Furusaki and Nagaosa on the basis of perturbative renormalization group calculations. For on-site Hubbard repulsion and ferromagnetic Kondo exchange, the ground state has spin S-1/2, i.e., is a singlet when S=1/2. The contributions of the impurity to the magnetic susceptibility and low-temperature specific heat are discussed. While the Wilson ratio is unity in the half-filled band, it is found to be a function of density and interaction away from half-filling.