Charge dynamics in the Mott insulating phase of the ionic Hubbard model

TL;DR

This paper investigates charge and bond dynamics in the ionic Hubbard model's Mott insulating phase, revealing how charge correlations decay despite a charge gap, due to charge-spin coupling effects.

Contribution

It extends the transformation to charge and bond operators and calculates charge density wave amplitudes across dimensions, highlighting unique decay behaviors.

Findings

Charge-charge correlations decay as 1/(d^3 ln^{3/2}d) in 1D.

Bond-bond correlations decay as (-1)^d 1/(d ln^{3/2}d).

Charge-spin coupling influences correlation decay despite the charge gap.

Abstract

We extend to charge and bond operators the transformation that maps the ionic Hubbard model at half filling onto an effective spin Hamiltonian. Using these operators we calculate the amplitude of the charge density wave in different dimensions. In one dimension, the charge-charge correlations at large distance d decay as 1/(d^3 ln^{3/2}d), in spite of the presence of a charge gap, as a consequence of remaining charge-spin coupling. Bond-bond correlations decay as (-1)^d 1/(d ln^{3/2}d) as in the usual Hubbard model.