Kondo--attractive-Hubbard model for the ordering of local magnetic moments in superconductors

TL;DR

This paper investigates how local magnetic moments interact with conduction electrons exhibiting on-site attraction, revealing a robust coexistence of magnetic order and superconductivity with a variable magnetic arrangement.

Contribution

It introduces a Kondo--attractive-Hubbard model and uses DMRG to analyze the coexistence of magnetic order and superconductivity in one dimension, connecting theory with experimental trends.

Findings

Coexistence of magnetic order and superconductivity is robust.

Magnetic arrangement varies continuously with coupling constants.

Characteristic wave vector k* depends strongly on coupling, explaining experimental trends.

Abstract

We consider local magnetic moments coupled to conduction electrons with on-site attraction, in order to discuss the interplay between pairing and magnetic order. We probe the ground state properties of this model on a one-dimensional lattice through pair binding energies and several correlation functions, calculated by means of density-matrix renormalization group. A phase diagram is obtained (for fixed electron density 1/3), from which we infer that coexistence between magnetic order and superconductivity is robust, at the expense of a continuous distortion of the magnetic arrangement of the local moments, as evidenced by a strong dependence of the characteristic wave vector k* with the coupling constants. This allows us to understand some trends of the coexistence, such as the influence of the rare earth on k*, as observed experimentally in the borocarbides.