Metal-insulator transition and phase separation in doped AA-stacked graphene bilayers

TL;DR

This paper studies how doping affects AA-stacked graphene bilayers, revealing a transition from antiferromagnetic insulator to metal with phase separation, and discusses potential electronic device applications.

Contribution

It introduces a mean field theory analysis of doping-induced phase transitions and phase separation in AA-stacked graphene bilayers.

Findings

Doped bilayers are antiferromagnetic insulators at half-filling.

Doping induces phase separation into insulator and metal regions.

High doping leads to a homogeneous metallic phase.

Abstract

We investigate the doping of AA-stacked graphene bilayers. Applying a mean field theory at zero temperature we find that, at half-filling, the bilayer is an antiferromagnetic insulator. Upon doping, the homogeneous phase becomes unstable with respect to phase separation. The separated phases are an undoped antiferromagnetic insulator and a metal with a non-zero concentration of charge carriers. At sufficiently high doping, the insulating areas shrink and disappear, and the system becomes a homogeneous metal. The conductivity changes drastically upon doping, so the bilayer may be used as a switch in electronic devices. The effects of finite temperature are also discussed.