Magnetic properties and Mott transition of the Hubbard model for weakly coupled chains on the anisotropic triangular lattice

Abstract: We investigate the magnetic properties and Mott transition in the Hubbard model for weakly coupled chains on the anisotropic triangular lattice. Taking into account 120$^\circ$ N\'eel, and collinear orderings, the magnetic phase diagram is studied at zero temperature and half-filling by the variational cluster approximation. We found that when the on-site Coulomb repulsion $U$ is relatively large, nonmagnetic insulator, which is a candidate of the spin liquid state, is realized for wide range of the interchain hopping from quasi two-dimensional to almost one-dimensional regime. When the interchain hopping is relatively large, this nonmagnetic insulator becomes magnetic states as $U$ decreases. For rather small interchain hopping, it changes to the paramagnetic metal, thus purely paramagnetic metal-insulator transition (Mott transition) takes place. Implications of our results for the Cs$_2$CuBr$_4$ and Cs$_2$CuCl$_4$ are discussed.