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

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.

10 pages, 7 figures

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• Electronic Instabilities of the AA-Honeycomb Bilayer
• Spin-valley half-metal in systems with Fermi surface nesting
• Magnetic field effects in electron systems with imperfect nesting
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• Antiferromagnetic ordering and excitonic pairing in the AA-stacked bilayer graphene
• Can bilayer graphene become a fractional metal?
• Competition of spatially inhomogeneous states in antiferromagnetic Hubbard model
• Magic radius of AA bilayer graphene quantum dot
• Ordering in SU(4)-symmetric model of AA bilayer graphene
• Stacking sensitive topological phases in a bilayer Kane-Mele-Hubbard model at quarter filling
• Coexistence of nematic superconductivity and spin density wave in magic-angle twisted bilayer graphene
• Superconductivity and spin density wave in AA stacked bilayer graphene
• Spin-density wave state in simple hexagonal graphite
• Canted antiferromagnetism and excitonic order in gated double-layer graphene
• Mean-field analysis of a Hubbard interaction on Bernal Bilayer Graphene
• Ordered states in AB bilayer graphene in SU(4)-symmetric model
• Applied electric and magnetic field effects on the bandgap formation and antiferromagnetic ordering in AA-stacked Bilayer Graphene