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Mardi 20 avril — 14:00 en salle de cours 204 2ème étage

Quantum disordered phase on the frustrated Honeycomb lattice

Daniel Cabra (La PLata, Argentine)

par - 20 avril 2010

We study the phase diagram of the Heisenberg model on the Honeycomb lattice with antiferromagnetic interactions up to third neighbors along the line $J_2=J_3$, where it describes the strong coupling limit of the Hubbard model at half-filling. Using the Schwinger boson technique followed by a mean field decoupling and exact diagonalization for finite systems we find an intermediate phase where quantum disorder is predicted in the strong quantum limit $(S=\frac12)$. Both techniques provide consistent results which allow us to predict the existence of an intermediate phase with a spin gap and short range N\’eel correlations. The relation of these results with recent experiments is discussed.