Exact diagonalization study of Mott transition in the Hubbard model on an anisotropic triangular lattice

TL;DR

This study uses exact diagonalization to analyze the Mott transition in the Hubbard model on an anisotropic triangular lattice, revealing a nonmagnetic insulating phase and comparing results with previous theories.

Contribution

It provides a detailed phase diagram of the Hubbard model on an anisotropic triangular lattice using finite-size exact diagonalization and twisted boundary conditions.

Findings

Identification of a nonmagnetic insulating phase

Evidence of a Mott transition via Drude weight and charge gap

Comparison with previous theoretical results

Abstract

We study Mott transition in the two-dimensional Hubbard model on an anisotropic triangular lattice. We use the Lanczos exact diagonalization of finite-size clusters up to eighteen sites, and calculate Drude weight, charge gap, double occupancy and spin structure factor. We average these physical quantities over twisted boundary conditions in order to reduce finite-size effects. We find a signature of the Mott transition in the dependence of the Drude weight and/or charge gap on the system size. We also examine the possibility of antiferromagnetic order from the spin structure factor. Combining these information, we propose a ground-state phase diagram which has a nonmagnetic insulating phase between a metallic phase and an insulating phase with antiferromagnetic order. Finally, we compare our results with those reported in the previous theoretical studies, and discuss the possibility of an unconventional insulating state.