Antiferromagnetic long range order in the uniform resonating valence bond state on square lattice

With extensive variational Monte Carlo simulation, we show that the uniform resonating valence bond state(U-RVB) on square lattice is actually antiferromagnetic long range ordered. The ordered moment is estimated to be $m\approx 0.17$. Finite size scaling analysis on lattice up to lattice size of $50\times 50$ shows that the spin structure factor at the antiferromagnetic ordering wave vector follows perfectly the $$\mathrm{S}${$\mathrm{q}$=(\pi,\pi)} \simeq S{0}+\alpha (1/L)^{5/4}$behavior,where$L$ is linear scale of the lattice. Such a behavior is quite unexpected from the slave Boson mean field treatment or the Gutzwiller approximation of the uniform RVB state.