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Dimerized phase and transitions in a spatially anisotropic square lattice antiferromagnet

Oleg A. Starykh·Leon Balents
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Abstract

We investigate the spatially anisotropic square lattice quantum antiferromagnet. The model describes isotropic spin-1/2 Heisenberg chains (exchange constant J) coupled antiferromagnetically in the transverse (J_\perp) and diagonal (J_\times), with respect to the chain, directions. Classically, the model admits two ordered ground states -- with antiferromagnetic and ferromagnetic inter-chain spin correlations -- separated by a first order phase transition at J_\perp=2J_\times. We show that in the quantum model this transition splits into two, revealing an intermediate quantum-disordered columnar dimer phase, both in two dimensions and in a simpler two-leg ladder version. We describe quantum-critical points separating this spontaneously dimerized phase from classical ones.

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Oleg A. Starykh, Leon Balents. 2004-02-03. Dimerized phase and transitions in a spatially anisotropic square lattice antiferromagnet. https://doi.org/10.1103/physrevlett.93.127202

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