Journal of Physics A Mathematical and General
Finite cell calculations of an antiferromagnetic spin chain with long-range interactions
Robert S. Botet, Rémi Jullien
Abstract
The ground state properties of the Heisenberg antiferromagnetic spin- 1 / 2 chain with interactions varying as (distance) -p are investigated from finite cell calculations. The gap between the ground state and the first excited state as well as the end-to-end spin correlation function have been calculated for finite open chains up to 14 spins and 12 spins respectively. Aided by first-order perturbation calculations near p=0, the authors can extrapolate the gap in the thermodynamic limit, and they find that the gap vanishes for every p not=0. From the analysis of the spin correlation function they find that long-range order exists for p<1 and does not exist for p>2. The existence of long-range order in the range 1<p<2 remains an open question.