Insulating behavior with spin and charge order in the ionic Hubbard model

TL;DR

This study uses dynamical mean-field theory to show that in the ionic Hubbard model with antiferromagnetic order, the system remains insulating across all interaction strengths, with coexisting charge and spin order.

Contribution

It demonstrates that including antiferromagnetic order in the ionic Hubbard model eliminates the metallic phase predicted by paramagnetic solutions, confirming insulating behavior at all interactions.

Findings

Spectral functions always exhibit an energy gap.

System remains insulating for all interaction strengths.

Charge density modulation coexists with antiferromagnetic order.

Abstract

Paramagnetic solutions of the ionic Hubbard model at half-filling in dimensions $D>2$ indicate that the band and the Mott insulator phases are separated by a metallic phase. We present zero-temperature dynamical mean-field theory solutions, which include antiferromagnetic long-range order, and show that the one-particle spectral functions always possess an energy gap and therefore the system is insulating for all interaction strengths. The staggered charge density modulation coexists with antiferromagnetic long-range order of N\'eel type.