Frustrated Heisenberg antiferromagnet on the honeycomb lattice: A candidate for deconfined quantum criticality

We study the ground-state (gs) phase diagram of the frustrated spin-1/2 J(1)-J(2)-J(3) antiferromagnet with J(2) = J(3) = kappa J(1) on the honeycomb lattice using coupled-cluster theory and exact diagonalization methods. We present results for the gs energy, magnetic order parameter, spin-spin correlation function, and plaquette valence-bond crystal (PVBC) susceptibility. We find a Neel antiferromagnetic (AFM) phase for kappa < kappa(c1) approximate to 0.47, a collinear striped AFM phase for kappa > kappa(c2) approximate to 0.60, and a paramagnetic PVBC phase for kappa(c1) less than or similar to kappa less than or similar to kappa(c2). The transition at kappa(c2) appears to be of first-order type, while that at kappa(c1) is continuous. Since the Neel and PVBC phases break different symmetries our results favor the deconfinement scenario for the transition at kappa(c1)