Article

Variational Monte Carlo Study Of A Gapless Spin Liquid In The Spin- 1/2 XXZ Antiferromagnetic Model On The Kagome Lattice

By using the variational Monte Carlo technique, we study the spin-12 XXZ antiferromagnetic model (with easy-plane anisotropy) on the kagome lattice. A class of Gutzwiller projected fermionic states with a spin Jastrow factor is considered to describe either spin liquids [with U(1) or Z2 symmetry] or magnetically ordered phases [with q=(0,0) or q=(4π/3,0)]. We find that the magnetic states are not stable in the thermodynamic limit. Moreover, there is no energy gain to break the gauge symmetry from U(1) to Z2 within the spin-liquid states, as previously found in the Heisenberg model. The best variational wave function is therefore the U(1) Dirac state, supplemented by the spin Jastrow factor. Furthermore, a vanishing S=2 spin gap is obtained at the variational level, in the whole regime from the XY to the Heisenberg model.

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