Metal-insulator transition in the disordered Hubbard model of the Lieb lattice

TL;DR

This study uses quantum Monte Carlo simulations to explore how disorder and interactions induce a metal-insulator transition in a Lieb lattice, revealing an Anderson insulator phase at specific electron densities.

Contribution

It demonstrates the combined effects of disorder and Coulomb interactions on the metal-insulator transition in a Lieb lattice, highlighting the emergence of an Anderson insulator away from half-filling.

Findings

Disorder and interactions induce a metal-insulator transition.

The system remains paramagnetic when doped.

Finite density of states at Fermi level indicates Anderson insulator.

Abstract

Using the determinant quantum Monte Carlo method, we investigate the metal-insulator transition in the interacting disordered Hubbard model of a Lieb lattice, in which the system characterizes the flat band centered at the Fermi level. By choosing suitable electron densities, we ensure the weak interaction sign problem to improve the reliability of our results. It is found that disorder and on-site Coulomb repulsive interaction produce interesting effects that induce the metal-insulator transition which is impossible in the half-filled case. The density of states at the Fermi energy is still finite in the thermodynamic limit, suggesting that the system is an Anderson insulator rather than a Mott insulator. Moreover, this doping system is paramagnetic, unlike the half-filled system, which is ferrimagnetic.