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arXiv · 1305.0330

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

A. O. Sboychakov·A. V. Rozhkov·A. L. Rakhmanov·Franco Nori
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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 paramagnetic to antiferromagnetic phase may demonstrate re-entrance. When disorder is present, phase separation could manifest itself as a percolative insulator-metal transition driven by doping.

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A. O. Sboychakov, A. V. Rozhkov, A. L. Rakhmanov, Franco Nori. 2013-05-02. Antiferromagnetic states and phase separation in doped AA-stacked graphene bilayers. https://doi.org/10.1103/physrevb.88.045409

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