Abstract
We present the results of extensive finite-temperature Quantum Monte Carlo simulati
ons on a SU(2) symmetric, $S=1/2$ quantum antiferromagnet with a frustrating four-s
pin interaction -- the so-called 'JQ' model~[Sandvik, Phys. Rev. Lett. {\bf 98}, 22
7202 (2007)]. Our simulations, which are unbiased, free of the sign-problem and car
ried out on lattice sizes containing in excess of $1.6\times 10^4$ spins, indicate
that N\'eel order is destroyed through a continuous quantum transition at a critica
l value of the frustrating interaction. At larger values of this coupling the param
agnetic state obtained has valence-bond solid order. The scaling behavior in the 'q
uantum critical fan' above the putative critical point confirms a $z=1$ quantum pha
se transition that is not in the conventional $O(3)$ universality class. Our result
s are consistent with the predictions of the 'deconfined quantum criticality' scena
rio.