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Critical behavior in quantum spin chains with composite spin

1989; American Physical Society; Volume: 39; Issue: 10 Linguagem: Inglês

10.1103/physrevb.39.7003

1095-3795

J. Sólyom, J. Timonen,

Quantum and electron transport phenomena

Composite spin models are constructed such that, by varying two parameters, they interpolate between the spin-(1/2 antiferromagnetic Heisenberg chain and a number of spin-1 models. These include the usual Heisenberg model, the integrable spin-1 model, and the model with an exact valence-bond ground state. Finite-chain calculations are performed on the composite spin model to study its criticality, and to find if the integrable spin-1 model is a multicritical point with a finite gap generated away from it. We find indications for an extended gapless region.