Strong-coupling perturbative study of the disordered Hubbard model on honeycomb lattice

TL;DR

This study investigates the disordered Hubbard model on a honeycomb lattice using strong-coupling perturbation theory, revealing a direct transition between Anderson and Mott insulators and interaction-dependent localization behaviors.

Contribution

It introduces a novel combination of strong-coupling perturbation theory with kernel polynomial and transfer matrix methods to study large disordered systems and finite size effects.

Findings

Direct transition between Anderson and Mott insulators at comparable disorder and interaction strengths.

Nonmonotonic localization length behavior with interaction strength.

Localization length becomes comparable to lattice scale at strong interactions.

Abstract

We study the Anderson disordered Hubbard model on the honeycomb lattice. The Hubbard term is han- dled with strong-coupling perturbation theory which encodes the Mott transition physics into a rich dynamical structure of a local self-energy. The local nature of self-energy allows us to combine it with kernel polynomial method and transfer matrix methods. The locality of self-energy combined with the analytic nature of the strong- coupling perturbation theory enables us to study lattices with millions of sites. The transfer matrix method in the ribbon geometry is essentially free from finite size errors and allows us to perform a careful finite size scaling of the width of the ribbon. This finite size scaling enables us to rule out the possibility of metallic phase in between the Mott and Anderson insulating phases. We therefore find a direct transition between Anderson and Mott insulators when the disorder strength W is comparable to the Hubbard interaction U . For a fixed disorder W , we obtain an interaction dependent nonmonotonic behavior of the localization length which reflects interac- tion induced enhancement of the localization length for weak and intermediate interaction strengths. Eventually at strong interactions U, the Mott localization takes over and the localization length becomes comparable to the lattice scale. This is reminiscent of the holographic determination of the Mott state where the system at IR recognizes its UV lattice scale.