Ferromagnetism and Metal-Insulator Transition in the Disordered Hubbard Model

TL;DR

This paper investigates how binary alloy disorder affects ferromagnetic phase transitions and metal-insulator behavior in the Hubbard model, revealing density-dependent effects on Curie temperature and a novel transition mechanism.

Contribution

It provides a detailed analysis of disorder effects on ferromagnetism and introduces a new type of metal-insulator transition driven by disorder and correlations.

Findings

Disorder reduces Curie temperature at high electron densities.

Disorder can enhance Curie temperature at low densities with strong interactions.

A new metal-insulator transition occurs at specific electron densities due to disorder and correlations.

Abstract

A detailed study of the paramagnetic to ferromagnetic phase transition in the one-band Hubbard model in the presence of binary alloy disorder is presented. The influence of the disorder (with concentration $x$ and $1-x$ of the two alloy ions) on the Curie temperature $T_{c}$ is found to depend strongly on electron density $n$. While at high densities, $n>x$, the disorder always reduces $T_c$, at low densities, $n<x$, the disorder can even \emph{enhance} $T_c$ if the interaction is strong enough. At the particular density $n=x$ (i. e. not necessarily at half filling) the interplay between disorder-induced band splitting and correlation induced Mott transition gives rise to a new type of metal-insulator transition.