Weak ferromagnetism and spiral spin structures in honeycomb Hubbard planes

Abstract

Within the Hartree Fock- RPA analysis, we derive the spin wave spectrum for the weak ferromagnetic phase of the Hubbard model on the honeycomb lattice. Assuming a uniform magnetization, the polar (optical) and acoustic branches of the spin wave excitations are determined. The bipartite lattice geometry produces a q-dependent phase difference between the spin wave amplitudes on the two sub-lattices. We also find an instability of the uniform weakly magnetized configuration to a weak antiferromagnetic spiraling spin structure, in the lattice plane, with wave vector Q along the Gamma-K direction, for electron densities n>0.6. We discuss the effect of diagonal disorder on both the creation of electron bound states, enhancement of the density of states, and the possible relevance of these effects to disorder induced ferromagnetism, as observed in proton irradiated graphite.

13 pages, 7 figures

References in corpus (15)

• Electric Field Effect in Atomically Thin Carbon Films
• Ultrathin epitaxial graphite: 2D electron gas properties and a route toward graphene-based nanoelectronics
• Induced Magnetic Ordering by Proton Irradiation in Graphite
• Non-Fermi liquid behaviour of electrons in the half-filled honeycomb lattice (A renormalization group approach)
• Fabrication and Electric Field Dependent Transport Measurements of Mesoscopic Graphite Devices
• Ferromagnetism in Oriented Graphite Samples
• Fractionalization in an Easy-axis Kagome Antiferromagnet
• Unconventional quasiparticle lifetime in graphite
• Reentrant Metallic Behavior of Graphite in the Quantum Limit
• Phase diagram and magnetic collective excitations of the Hubbard model in graphene sheets and layers
• Disorder Induced Ferromagnetism in CaRuO3
• Diluted quantum antiferromagnets: spin excitations and long-range order
• T-Matrix Formulation of Impurity Scattering in Correlated Systems
• Long-range order and low-energy spectrum of diluted 2D quantum AF
• Weak ferromagnetism and spiral spin structures in honeycomb Hubbard planes

Cited by in corpus (8)

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• Colloquium: The transport properties of graphene: An introduction
• Massive Dirac fermions in single-layer graphene
• Nonmagnetic-Defect-Induced Magnetism in Graphene
• Pomeranchuk instability in doped graphene
• Defect Induced Resonances and Magnetic Patterns in Graphene
• Weak ferromagnetism and spiral spin structures in honeycomb Hubbard planes
• First order ferromagnetic phase transition in the low electronic density regime of a biased graphene bilayer