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

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 t...

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Bibliographic Details
Published in:Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2013-07, Vol.88 (4), Article 045409
Main Authors: Sboychakov, A. O., Rozhkov, A. V., Rakhmanov, A. L., Nori, Franco
Format: Article
Language:English
Subjects:
Antiferromagnetism
Condensed matter
Disorders
Doping
Fermi level
Fermi surfaces
Graphene
Phase separation
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Summary: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.
ISSN:1098-0121
1550-235X
DOI:10.1103/PhysRevB.88.045409