We investigate the magnetic and metal-insulator (M-I) phase diagram of the 15-depleted square-lattice Hubbard model at 14 filling by the mean-field approximation. There exist three magnetic phases of nonmagnetic (N), antiferromagnetic (AF), and ferromagnetic (F) types, each realized for the large intrasquare hopping t1, intersquare hopping t2, and Coulomb interaction U, respectively. Within each magnetic phase, the M-I transition of Lifshitz type emerges and, finally, six kinds of phases are identified in the U-t1/t2 plane. When t1=t 2, we find that the Dirac cone and nearly flat band around the Γ point form the SU(3) multiplet. The SU(3) effective theory well describes the phase transitions between NI, paramagnetic-metal (PM), and AF phases. The NI and AFI phases are characterized by different Berry phases as in polyacetylene or graphene.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2013 Nov 4|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics