title: Quantum disordered phase near the Mott transition in the staggered-flux Hubbard model on a square lattice.
abstract: We investigate ground state properties of the half-filled staggered-flux Hubbard model on a square lattice. Energy gaps to charge and spin excitations and magnetic as well as dimer orders are calculated as a function of interaction strength U/t by means of a constrained-path quantum Monte Carlo method. It is found that the system is a semimetal at U/t≲5.6 and a Mott insulator, with long-range antiferromagnetic order, at U/t≳6.6. In the range 5.6≲U/t≲6.6, the ground state is a correlated insulator where both magnetic and dimer orders are absent. Furthermore, spin excitation in the intermediate phase appears to be gapless, and the measured spin-spin correlation function exhibits power-law decaying behavior. The data suggest that the nonmagnetic ground state is a possible candidate for the putative algebraic spin liquid.
authors.affiliation: Department of Physics, University of California, Davis, Davis, California 95616, USA.
authors.forename: Chia-Chen
authors.initials: CC
authors.lastname: Chang
authors.forename: Richard T
authors.initials: RT
authors.lastname: Scalettar