Charge gaps and quasiparticle bands of the ionic Hubbard model

TL;DR

This paper investigates the ionic Hubbard model on a cubic lattice, analyzing charge gaps and quasiparticle bands near the Mott insulator regime using analytical methods and renormalization group techniques.

Contribution

It provides a detailed analysis of the charge excitation spectrum and spectral weights, highlighting the hybridization mechanism and charge gap formation at half-filling.

Findings

Narrow charge gap at half-filling

Spectral weights reflect hybridization

Agreement with hybridized-band picture

Abstract

The ionic Hubbard model on a cubic lattice is investigated using analytical approximations and Wilson's renormalization group for the charge excitation spectrum. Near the Mott insulating regime, where the Hubbard repulsion starts to dominate all energies, the formation of correlated bands is described. The corresponding partial spectral weights and local densities of states show characteristic features, which compare well with a hybridized-band picture appropriate for the regime at small $U$, which at half-filling is known as a band insulator. In particular, a narrow charge gap is obtained at half-filling, and the distribution of spectral quasi-particle weight reflects the fundamental hybridization mechanism of the model.