Quantum Phase transitions in Hubbard lattices

We investigate the quantum phase transitions in the half-filled Hubbard model on the triangular lattice by means of the path-integral renormalization group (PIRG) method with a new iteration scheme proposed recently. It is found that as the Hubbard interaction $U$ increases, the paramagnetic metallic state undergoes a first-order phase transition to a nonmagnetic insulating (NMI) state at $U_{c1}\sim 7.7t$ , which is followed by another first-order transition to a $120^\circ$ Néel ordered state at $U_{c2}\sim 10t$ , where $t$ is the transfer integral. Our results ensure the existence of the intermediate NMI phase, and resolve some controversial arguments on the nature of the previously proposed quantum phase transitions. We find that $κ$ -(BEDT-TTF) $_2$ Cu $_2$ (CN) $_3$ is located in the NMI phase close to the metal-insulator transition point.We investigate the quantum phase transitions in the half-filled Hubbard model on the triangular lattice by means of the path-integral renormalization group (PIRG) method with a new iteration scheme proposed recently. It is found that as the Hubbard interaction $U$ increases, the paramagnetic metallic state undergoes a first-order phase transition to a nonmagnetic insulating (NMI) state at $U_{c1}\sim 7.7t$, which is followed by another first-order transition to a $120^\circ$ Néel ordered state at $U_{c2}\sim 10t$, where $t$ is the transfer integral. Our results ensure the existence of the intermediate NMI phase, and resolve some controversial arguments on the nature of the previously proposed quantum phase transitions. We find that $κ$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ is located in the NMI phase close to the metal-insulator transition point.

arXiv:0811.1575Nov 10, 20081 citation

U

increases, the paramagnetic metallic state undergoes a first-order phase transition to a nonmagnetic insulating (NMI) state at

U_{c1}\sim 7.7t

, which is followed by another first-order transition to a

120^\circ

Néel ordered state at

U_{c2}\sim 10t

, where

t

is the transfer integral. Our results ensure the existence of the intermediate NMI phase, and resolve some controversial arguments on the nature of the previously proposed quantum phase transitions. We find that

κ

-(BEDT-TTF)

_2

_2

(CN)

_3

is located in the NMI phase close to the metal-insulator transition point.