I will discuss the valence-bond-solid (VBS) phase and the Neel-VBS quantum phase transition in a 2D S=1/2 Heisenberg model which in addition to the standard nearest-neighbor exchange includes a four-spin interaction (a subset of the fours-spin cyclic exchange terms). Quantum Monte Carlo simulations, carried out in the valence bond basis, show evidence for deconfined quantum criticality in this model. As predicted theoretically, the spin correlation exponent eta is anomalously large and there are explicit signs of an emergent U(1) symmetry at the critical point.
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