Effects of correlations on honeycomb lattice in ionic-Hubbard Model

TL;DR

This study investigates how electron-electron interactions and ionic potential influence the energy gap and electronic properties of a honeycomb lattice, revealing phase transitions and effects relevant to gapped graphene.

Contribution

It applies dynamical mean field theory with iterative perturbation to analyze the interplay of $U$ and $ abla$ on the honeycomb lattice's electronic phases, a novel approach for this system.

Findings

Competition between $U$ and $ abla$ closes and reopens the energy gap.

Renormalized Fermi velocity decreases with increasing $U$.

Filling factor varies with $U$ and $ abla$.

Abstract

In a honeycomb lattice the symmetry has been broken by adding an ionic potential and a single-particle gap was generated in the spectrum. We have employed the iterative perturbation theory (IPT) in dynamical mean field approximation method to study the effects of competition between $U$ and $\Delta$ on energy gap and renormalized Fermi velocity. We found, the competition between the single-particle gap parameter and the Hubbard potential closed the energy gap and restored the semi-metal phase, then the gap is opened again in Mott insulator phase. For a fixed $\Delta$ by increasing $U$, the renormalized Fermi velocity $\tilde{v_F}$ is decreased, but change in $\Delta$, for a fixed $U$, has no effects on $\tilde{v_F}$. The difference in filling factor is calculated for various number of $U, ~\Delta$. The results of this study can be implicated for gapped graphene e.g. hydrogenated graphene.