An intermediate phase induced by dilution in a correlated Dirac Fermi system

TL;DR

This study uses quantum Monte Carlo simulations to reveal a novel intermediate insulating phase in a diluted Dirac fermion system, highlighting the complex interplay between dilution and electron interactions.

Contribution

It introduces the concept of a dilution-induced intermediate phase in correlated Dirac systems, supported by comprehensive numerical analysis.

Findings

Emergence of a nonmagnetic insulating phase due to dilution.

Robustness of the intermediate phase across various interaction strengths.

Doping nonmagnetic ions can revert the system to a metallic state.

Abstract

Substituting magnetic ions with nonmagnetic ions is a new way to study dilution. Using determinant quantum Monte Carlo calculations, we investigate an interacting Dirac fermion model with the on-site Coulomb repulsion being randomly zero on a fraction $x$ of sites. Based on conductivity, density of states and antiferromagnetic structure factor, our results reveal a novel intermediate insulating phase induced by the competition between dilution and repulsion. With increasing doping level of nonmagnetic ions, this nonmagnetic intermediate phase is found to emerge from the zero-temperature quantum critical point separating a metallic and a Mott insulating phase, whose robustness is proven over a wide range of interactions. Under the premise of strongly correlated materials, we suggest that doping nonmagnetic ions can effectively convert the system back to the paramagnetic metallic phase. This result not only agrees with experiments on the effect of dilution on magnetic order but also provides a possible direction for studies focusing on the metal-insulator transition in honeycomb lattice like materials.