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

TL;DR

This study explores the magnetic phases and Mott transition in the Hubbard model on an anisotropic triangular lattice, revealing a range of nonmagnetic insulators, magnetic states, and metallic phases depending on interaction strength and interchain coupling.

Contribution

It provides a detailed phase diagram for the Hubbard model on an anisotropic triangular lattice, highlighting the emergence of spin liquid states and transitions influenced by interchain hopping.

Findings

Nonmagnetic insulator (spin liquid candidate) exists over a wide range of parameters.

Magnetic states emerge as interchain hopping increases and U decreases.

Purely paramagnetic metal-insulator transition occurs at small interchain hopping.

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.