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Accueil du site > Publications > Publications 2011 > Phase Diagram of a Frustrated Quantum Antiferromagnet on the Honeycomb Lattice : Magnetic Order versus Valence-Bond Crystal formation

Phase Diagram of a Frustrated Quantum Antiferromagnet on the Honeycomb Lattice : Magnetic Order versus Valence-Bond Crystal formation

A.F. Albuquerque, D. Schwandt, B. Hetényi, S. Capponi, M. Mambrini, A.M. Läuchli

par Sylvain Capponi - 28 février 2011

We present a comprehensive computational study of the phase diagram of the frustrated S=1/2 Heisenberg antiferromagnet on the honeycomb lattice, with second-nearest (J_2) and third-neighbor (J_3) couplings. Using a combination of exact diagonalizations of the original spin model, of the Hamiltonian projected into the nearest neighbor short range valence bond basis, and of an effective quantum dimer model, as well as a self-consistent cluster mean-field theory, we determine the boundaries of several magnetically ordered phases in the the region J_2,J_3\in [0,1], and find a sizable magnetically disordered region in between. We characterize this magnetically disordered phase as a plaquette valence bond crystal phase. Furthermore we find that a particular parameter-free Gutzwiller projected tight-binding wave function has remarkably accurate energies compared to finite-size extrapolated ED energies along the transition line from conventional Néel to plaquette VBC phases, a fact that points to possibly interesting critical behavior across the transition.