Method of anomalous Green's functions: Antiferromagnetism in the Hubbard model on a triangular lattice

A method is proposed for describing antiferromagnetic and ferromagnetic states on a triangular lattice in the formalism of anomalous temperature-dependent Green's functions, for which equations of Dyson–Gor'kov type are formulated. These equations are solved in the Hartree approximation, and self-consistency equations are obtained for the order parameters. Finally, the connection between the considered theory and experiment is discussed.