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Plaquette order on the honeycomb lattice

Frustrated magnetism often gives rise to many body states with various levels of entanglement. Recently, such a novel state consisting of entangled plaquettes has been proposed in the honeycomb lattice J1-J2 model. We use DMRG calculations, supported by semi-analytical methods, to study the ground state of this model.
First, using DMRG and non-linear spin wave theory, we show that quantum fluctuations stabilize Neel order beyond its classical domain of stability. We then study the putative plaquette-RVB state using a plaquette-operator approach. Assuming a plaquette-RVB ground state, we calculate properties such as spin gap, ground state state energy, etc. Our predictions can be tested using DMRG or Quantum Monte Carlo methods.