Mott transition and magnetism of the triangular-lattice Hubbard model with next-nearest-neighbor hopping

Abstract

The variational cluster approximation is used to study the isotropic triangular-lattice Hubbard model at half filling, taking into account the nearest-neighbor ($t_1$) and next-nearest-neighbor ($t_2$) hopping parameters for magnetic frustrations. We determine the ground-state phase diagram of the model. In the strong correlation regime, the 120${}^{\circ }$ Néel and stripe ordered phases appear, and a nonmagnetic insulating phase emerges in between. In the intermediate correlation regime, the nonmagnetic insulating phase expands to a wider parameter region, which goes into a paramagnetic metallic phase in the weak correlation regime. The critical phase boundary of the Mott metal-insulator transition is discussed in terms of the van Hove singularity evident in the calculated density of states and single-particle spectral function.

8 pages, 9 figures. Phys. Rev. B, in press

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• Uncovering double-stripe and plaquette antiferromagnetic states in the one-band Hubbard model on a frustrated square lattice
• Reentrance of metal-insulator transition and magnetic competitions on a triangular lattice with second nearest-neighbor hopping