Volume 87, Number 6, September 2009
Article Number 67002
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 06 October 2009
EPL, 87 (2009) 67002
DOI: 10.1209/0295-5075/87/67002

Quantum non-magnetic state near metal-insulator transition —A possible candidate of spin liquid state

Gao-Yong Sun and Su-Peng Kou

Department of Physics, Beijing Normal University - Beijing 100875, China

received 17 June 2009; accepted in final form 8 September 2009; published September 2009
published online 6 October 2009

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.

71.10.Fd - Lattice fermion models (Hubbard model, etc.).
71.10.Hf - Non-Fermi-liquid ground states, electron phase diagrams and phase transitions in model systems.
75.10.-b - General theory and models of magnetic ordering.

© EPLA 2009