Spectral-weight function of the ionic Hubbard model

TL;DR

This paper investigates the spectral-weight function of the half-filled ionic Hubbard model using Quantum Monte Carlo, revealing a metallic phase between band insulator and antiferromagnetic insulator states, with a complex evolution of spectral features.

Contribution

It provides the first detailed Quantum Monte Carlo analysis of the spectral-weight function in the ionic Hubbard model, identifying the conditions for metallic, band insulator, and antiferromagnetic insulator phases.

Findings

Metallic phase exists between U1 and U2.

Spectral peaks approach and overlap during the transition.

System evolves from band insulator to Mott insulator.

Abstract

The one-electron spectral-weight function of the half-filled ionic Hubbard model is calculated by means of Quantum Monte Carlo. A metallic regimen occurs between two values of the coupling constant (Hubbard U) U1 < U2 . The system is a band insulator below U1, and an increasingly antiferromagnetic (AF) insulator above U2 evolving into a Mott insulator as U tends to infinity . The intermediate regimen which is both AF and dimerized, is caused by a two-peak structure at k = 0,5 pi (the Fermi surface). As U increases both peaks approach each other, overlap, and separate again, the system becoming metallic in the overlap region.