Quantum Non-Magnetic state near Metal-Insulator Transition - a Possible Candidate of Spin Liquid State

TL;DR

This paper investigates a quantum non-magnetic insulator near the metal-insulator transition in a 2D Pi-flux Hubbard model, proposing it as a potential spin liquid state driven by quantum fluctuations, not frustration.

Contribution

It introduces a non-linear sigma model approach to identify a quantum non-magnetic insulator as a candidate for a spin liquid state without frustration effects.

Findings

Quantum non-magnetic insulator identified near transition

Results consistent with previous strong-coupling calculations

Proposes a spin liquid state driven by quantum fluctuations

Abstract

In this paper, based on the formulation of an O(3) non-linear sigma model, we study the two-dimensional Pi-flux Hubbard model at half-filling. A quantum non-magnetic insulator is explored near the metal-insulator transition that may be a possible candidate of the spin liquid state. Such quantum non-magnetic insulator on square lattice is not induced by frustrations. Instead, it originates from quantum spin fluctuations with relatively small effective spin moments. In the strong-coupling limit, our results of the spin velocity and spin order parameter agree with results obtained from earlier calculations.