Ordered states in the disordered Hubbard model

TL;DR

This study explores how disorder affects magnetic order and charge gaps in the Hubbard model, revealing that disorder can enhance antiferromagnetic order and split the Mott-Hubbard gap into distinct states.

Contribution

It demonstrates that disorder can stabilize antiferromagnetic order and modify the charge gap structure in the Hubbard model, using Quantum Monte Carlo and DMFT methods.

Findings

Disorder initially enhances antiferromagnetic order.

The Mott-Hubbard gap splits into two parts due to disorder.

An incompressible state persists at half-filling.

Abstract

The Hubbard model is studied in which disorder is introduced by putting the on-site interaction to zero on a fraction f of (impurity) sites of a square lattice. Using Quantum Monte Carlo methods and Dynamical Mean Field theory we find that antiferromagnetic long-range order is initially enhanced at half-filling and stabilized off half-filling by the disorder. The Mott-Hubbard charge gap of the pure system is broken up into two pieces by the disorder: one incompressible state remains at average density n=1 and another can be seen slightly below n=1+f. Qualitative explanations are provided.