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Accueil du site > Publications > Publications 2006 > Plaquette valence bond crystal in the frustrated Heisenberg quantum antiferromagnet on the square lattice

Plaquette valence bond crystal in the frustrated Heisenberg quantum antiferromagnet on the square lattice

Matthieu Mambrini, Andreas Läuchli, Didier Poilblanc and Frédéric Mila

par Matthieu Mambrini - 30 juin 2006

Using both exact diagonalizations and diagonalizations in a subset of short-range valence bond singlets, we address the nature of the groundstate of the Heisenberg spin-1/2 antiferromagnet on the square lattice with competing next-nearest and next-next-nearest neighbor antiferromagnetic couplings (J_1 - J_2 - J_3 model). A detailed comparison of the two approaches reveals a region along the line (J_2+J_3)/J_1=1/2, where the description in terms of nearest-neighbor singlet coverings is excellent, therefore providing evidence for a magnetically disordered region. Furthermore a careful analysis of dimer-dimer correlation functions, dimer structure factors and plaquette-plaquette correlation functions provides striking evidence for the presence of a plaquette valence bond crystal order in part of the magnetically disordered region.