The phase-diagram of the Blume-Capel-Haldane-Ising spin chain

03/15/2016 - 15:30
03/15/2016 - 16:30
Manu Paranjape, GPP, Département de physique
CRM, UdeM, Pavillon André-Aisenstadt, 2920, ch. de la Tour, salle 4336

 We consider the one-dimensional spin chain for arbitrary spin $s$ on a periodic chain with $N$ sites, the generalization of the chain that was studied by Blume and Capel cite{bc}: $$H=sum_{i=1}^N left(a (S^z_i)^2+ b S^z_iS^z_{i+1} ight).$$ Although the Hamiltonian is trivially diagonal, it is actually not always obvious which eigenstate is the ground state. We show how to find the ground state for all regions of the parameter space and thus determine the phase diagram of the model. We observe the existence of solitons-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 $N$ and not on boundary conditions.

Last edited by on Thu, 03/10/2016 - 15:52