Metal-Insulator Transition of Dirac Fermions: Variational Cluster Study

TL;DR

This study investigates the metal-insulator transition of Dirac fermions in honeycomb and -flux Hubbard models using variational cluster methods, confirming a direct transition without an intermediate spin liquid phase.

Contribution

It demonstrates that the direct transition from Dirac semimetal to antiferromagnetic Mott insulator occurs, clarifying the nature of the phase transition in these models.

Findings

Direct transition from Dirac semimetal to Mott insulator confirmed

Spin liquid phase is absent in the intermediate region

Results agree with recent quantum Monte Carlo studies

Abstract

A comparative study is made on the metal-insulator transition of Dirac fermions in the honeycomb and \pi-flux Hubbard models at half filling by means of the variational cluster approximation and cluster dynamical impurity approximation. Paying particular attention to the choice of the geometry of solver clusters and the inclusion of particle-bath sites, we show that the direct transition from the Dirac semimetallic state to the antiferromagnetic Mott insulator state occurs in these models, and therefore, the spin liquid phase is absent in the intermediate region, in agreement with recent quantum-Monte-Carlo--based calculations.