Speaker
Christian Boudreault
(Collège militaire royal de Saint-Jean / Université de Montréal)
Description
We consider the one-dimensional spin chain for arbitrary spin s on a periodic chain with N sites,
H = \sum_i^N ( a (S_i^z)^2 + b S_i^z S_{i+1}^z ),
the generalization of the chain that was studied by Blume and Capel. The Hamiltonian only involves the z component of the spin thus it is essentially an Ising model. The Hamiltonian also figures exactly as the anisotropic term in the famous model studied by Haldane of the large spin Heisenberg spin chain. Therefore we call the model the Blume-Capel-Haldane-Ising model. Although the Hamiltonian is trivially diagonal, it is actually not always obvious which eigenstate is the ground state. In this presentation we establish which state is the ground state for all regions of the parameter space and thus determine the phase diagram of the model. We observe the existence of massless soliton-like excitations and we show that the size of the solitons depends only on the ratio a/b and not on the number of sites N.
Authors
Christian Boudreault
(Collège militaire royal de Saint-Jean / Université de Montréal)
Manu Paranjape
(Université de Montréal)
Solomon Akaraka Owerre
