A lattice model for the SU(N) Neel-VBS quantum phase transition at large N

We generalize the SU(N=2) $S=1/2$ square-lattice quantum magnet with nearest-neighbor antiferromagnetic coupling ($J_1$) and next-nearest-neighbor ferromagnetic coupling ($J_2$) to arbitrary $N$. For all $N>4$, the ground state has valence-bond-solid (VBS) order for $J_2=0$ and Néel order for $J_2/J_1\gg 1$, allowing us access to the transition between these types of states for large $N$. Using quantum Monte Carlo simulations, we show that both order parameters vanish at a single quantum-critical point, whose universal exponents for large enough $N$ (here up to N=12) approach the values obtained in a 1/N expansion of the non-compact CP$^{N-1}$ field theory. These results lend strong support to the deconfined quantum-criticality theory of the Néel--VBS transition.

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