Antiferromagnetic states and phase separation in doped AA-stacked graphene bilayers

A. O. Sboychakov, A. V. Rozhkov, A. L. Rakhmanov, Franco Nori

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

We study electronic properties of AA-stacked graphene bilayers. In the single-particle approximation such a system has one electron band and one hole band crossing the Fermi level. If the bilayer is undoped, the Fermi surfaces of these bands coincide. Such a band structure is unstable with respect to a set of spontaneous symmetry violations. Specifically, strong on-site Coulomb repulsion stabilizes antiferromagnetic order. At small doping and low temperatures, the homogeneous phase is unstable and experiences phase separation into an undoped antiferromagnetic insulator and a metal. The metallic phase can be either antiferromagnetic (commensurate or incommensurate) or paramagnetic depending on the system parameters. We derive the phase diagram of the system on the doping-temperature plane and find that, under certain conditions, the transition from the paramagnetic to the antiferromagnetic phase may demonstrate reentrance. When disorder is present, phase separation could manifest itself as a percolative insulator-metal transition driven by doping.

Original languageEnglish
Article number045409
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume88
Issue number4
DOIs
Publication statusPublished - 8 Jul 2013
Externally publishedYes

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